Electronic device and communication method

Abstract

To provide an electronic device and a communication method capable of communicating a subsequent peripheral device daisy-chained from a body, even if power supplied to a peripheral device daisy-chained from the body is cut off.SOLUTION: An electronic device includes a first substrate, a second substrate that receives power supplied from the first substrate, a third substrate that receives power supplied from the second substrate, a first control apparatus which controls operation of the first substrate, a second control apparatus which controls operation of the second substrate and communicates with the first control apparatus, a third control apparatus which controls operation of the third substrate and communicates with the second control apparatus, cut-off means which cuts off power when overcurrent occurs in the second substrate, detection means which detects power cut-off, and switching means which switches between a communication path through which the first control apparatus communicates with the second control apparatus and a communication path through which the first control apparatus communicates with the third control apparatus. The switching means selects the communication path for the communication between the first control apparatus and the third control apparatus when the power cut-off is detected.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electronic device and a communication method. [Background technology]

[0002] When an electronic device is equipped with optional devices, a known technology is for the main control board that controls the electronic device itself to supply power to another control board (peripheral control board) that controls the optional devices, and for these to communicate via connection via a cable, harness, etc. This type of system in which multiple units are connected in series via a cable, harness, etc. is generally referred to as a daisy chain connection.

[0003] As a technology configured in a daisy chain from such a main unit, a technology has been disclosed in which a sub-CPU is reset when the sub-CPU goes into an abnormal state, in order to be able to respond appropriately to unexpected abnormalities in equipment having a control unit configured across multiple boards (for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional technology, when peripheral devices are connected to the main unit in a daisy chain, if the fuse of a peripheral device connected to the main unit blows, communication with all subsequent peripheral devices connected in the daisy chain becomes impossible.

[0005] The present invention has been made in consideration of the above, and aims to provide an electronic device and a communication method that can communicate with a subsequent peripheral device connected in a daisy chain from the main body even if the power supply to the peripheral device connected in a daisy chain from the main body is cut off. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the present invention provides a power supply system comprising a first board, a second board receiving power from the first board, a third board receiving power from the second board, a first control device mounted on the first board and controlling the operation of the first board, a second control device mounted on the second board and controlling the operation of the second board and communicating with the first control device, a third control device mounted on the third board and controlling the operation of the third board and communicating with the second control device, a cut-off means provided on the second board for cutting off the power supply from the first board when an overcurrent occurs on the second board, a detection means provided on the second board for detecting that the power has been cut off by the cut-off means, and a switching means provided on the second board for switching between a communication path between the first control device and the second control device and a communication path between the first control device and the third control device, wherein the switching means switches to the communication path between the first control device and the third control device when the detection means detects that the power has been cut off by the cut-off means. [Effects of the Invention]

[0007] According to the present invention, even if the power supply to a peripheral device connected in a daisy chain from the main unit is cut off, the main unit can still communicate with a subsequent peripheral device connected in a daisy chain. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of a circuit configuration of a main body control board and a peripheral device control board of an electronic device according to an embodiment. [Figure 2] FIG. 2 is a diagram showing a circuit configuration of the electronic device according to the embodiment in a normal state. [Figure 3] FIG. 3 is a diagram showing a circuit configuration of the electronic device according to the embodiment in a state where a fuse is blown. [Figure 4] FIG. 4 is a timing chart showing an example of a communication operation between the main body control board and the peripheral device control board of the electronic device according to the embodiment. [Figure 5]FIG. 5 is a diagram showing a configuration in which peripheral device control boards are connected in multiple stages to a main body control board in a daisy chain connection in an electronic device according to an embodiment. [Figure 6] FIG. 6 is a flowchart showing an example of the flow of operations of the main SoC of the electronic device according to the embodiment. [Figure 7] FIG. 7 is a diagram showing an example of the circuit configuration of a main body control board and a peripheral device control board of an electronic device according to the first modification. [Figure 8] FIG. 8 is a diagram showing an example of the circuit configuration of a main body control board and a peripheral device control board of an electronic device according to the second modification. [Figure 9] FIG. 9 is a diagram showing an example of the circuit configuration of a main body control board and a peripheral device control board of an electronic device according to the third modification. [Figure 10] FIG. 10 is a diagram showing an example of the circuit configuration of a main body control board and a peripheral device control board of an electronic device according to the fourth modification. [Figure 11] FIG. 11 is a diagram showing an example of the circuit configuration of a main body control board and a peripheral device control board of an electronic device according to the fifth modification. [Figure 12] FIG. 12 is a diagram showing an example of the circuit configuration of a main body control board and a peripheral device control board of an electronic device according to the sixth modification. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of an electronic device and a communication method according to the present invention will be described in detail with reference to the drawings. Furthermore, the present invention is not limited to the following embodiments, and the components in the following embodiments include those that would be easily conceived by a person skilled in the art, those that are substantially the same, and those that are within the scope of what is called equivalents. Furthermore, various omissions, substitutions, modifications, and combinations of the components can be made without departing from the spirit of the following embodiments.

[0010] [First embodiment] (Circuit configuration of electronic devices) 1 is a diagram showing an example of the circuit configuration of a main body control board and a peripheral device control board of an electronic device according to an embodiment. With reference to FIG. 1, the circuit configuration of a main body control board 10 and peripheral device control boards 20 and 30 of an electronic device 1 according to this embodiment will be described.

[0011] The electronic device 1 shown in FIG. 1 includes a main body control board 10 for controlling the main body of the electronic device 1, and peripheral control boards 20 and 30 for controlling other devices mounted on the electronic device 1, such as optional devices. In the example of the electronic device 1 shown in FIG. 1, the peripheral control board 20 and the peripheral control board 30 are connected in series in this order via a daisy chain connection from the main body control board 10, and data communication is performed between them via two-wire serial communication (hereinafter sometimes simply referred to as serial communication) using a UART (Universal Asynchronous Receiver Transmitter) communication method. In other words, such daisy chain connection allows the main body control board 10 and the peripheral control board 20 to communicate with each other, and the peripheral control board 20 and the peripheral control board 30 to communicate with each other. In other words, data communication between the main body control board 10 and the peripheral control board 30 is performed via the peripheral control board 20. Examples of the electronic device 1 include general electronic devices such as image forming devices, image reading devices, and projectors. If the electronic device 1 is, for example, an image forming device, the peripheral control boards 20 and 30 correspond to banks that are, for example, paper feeders, and if these banks are stacked under the image forming device main body, they are connected in a daisy chain. The main body control board 10, the peripheral control board 20, and the peripheral control board 30 correspond to the "first board," "second board," and "third board" of the present invention, respectively.

[0012] 1, the main body control board 10 includes a main SoC (System on a Chip) 101, a switching element 111, an IC circuit 112, connectors 121, 122, 131, and 132, and a resistor R1. Note that the main body control board 10 may be equipped with other components in addition to the components shown in FIG.

[0013] The main SoC 101 is a computing device that controls the entire main body control board 10. The main SoC 101 operates by receiving power from a power supply 140. Of the input / output ports that the main SoC 101 has, a transmission port, port Tx, and a reception port, port Rx, are assigned to perform serial communication with the peripheral device control board 20. In other words, the main SoC 101 of the main body control board 10 and a sub-SoC 201 (described later) perform data communication via two-wire asynchronous serial communication.

[0014] Instead of the main SoC 101, a computing device such as a microcontroller (MCU: Micro Control Unit) may be used.

[0015] The switching element 111 is driven by the output of the port Tx of the main SoC 101 and has an open-drain or open-collector output format. For example, if the switching element 111 is a FET (Field Effect Transistor), it has an open-drain output format, and if the switching element 111 is a transistor, it has an open-collector output format. The output terminal (drain or collector) of the switching element 111 is connected to the connector 121.

[0016] The IC circuit 112 has an input side connected to the connector 122 and an output side connected to the port Rx of the main SoC 101, and is an IC circuit that performs buffering and noise reduction of signals received from the sub SoC 201.

[0017] The connector 121 is a transmitting connector for outputting a signal transmitted from the port Tx of the main SoC 101 from the main body control board 10 in serial communication between the main SoC 101 and the sub SoC 201. The connector 121 is connected to a connector 221 (described later) of the peripheral device control board 20 by a communication line.

[0018] The connector 122 is a receiving connector for inputting a signal received at a port Rx of the main SoC 101 from the peripheral device control board 20 in serial communication between the main SoC 101 and the sub SoC 201. The connector 122 is connected to a connector 222 (described later) of the peripheral device control board 20 by a communication line.

[0019] The connector 131 is a power connector for supplying power from a power supply 140, which is a 5V power supply in the main body control board 10, to the peripheral device control board 20 and the peripheral device control board 30. The connector 131 is connected to a connector 231 (described later) of the peripheral device control board 20 by a power line.

[0020] The connector 132 is a connector for FG (frame ground), and is connected to a connector 232 (described later) of the peripheral device control board 20 by an FG line.

[0021] Resistor R1 is a pull-up resistor for pulling up the receive line of port Rx of main SoC 101 with a 5V power supply based on power supply 140. In this case, even if the power supply of main SoC 101 is not 5V, for example, communication can be performed by converting the voltage level.

[0022] The power supply 140 is a 5V power supply for supplying power to each device on the main body control board 10. The power supply 140 may be formed by being supplied with a 5V voltage directly from the outside, or may be formed by stepping down a predetermined voltage (for example, 24V) to 5V using a DC converter or the like mounted on the main body control board 10.

[0023] 1, the peripheral device control board 20 includes a sub-SoC 201, an IC circuit 211, a switching element 212, connectors 221, 222, 231, 232, a switching element 241, an IC circuit 242, connectors 251, 252, a fuse 272, connectors 261, 262, a detection circuit 290, resistors R2, R3, a selector switch 291, and a selector switch 292. The peripheral device control board 20 may be equipped with other components in addition to the components shown in FIG. 1. The selector switches 291 and 292 correspond to the "switching means" of the present invention.

[0024] The sub-SoC 201 is a computing device that controls the entire peripheral device control board 20. The sub-SoC 201 operates by receiving power from a power supply 271, which will be described later. Of the input / output ports that the sub-SoC 201 has, a transmission port, port Tx, and a reception port, port Rx, are assigned for serial communication with the main body control board 10. That is, the main SoC 101 of the main body control board 10 and the sub-SoC 201 communicate data using two-wire asynchronous serial communication. Also, of the input / output ports that the sub-SoC 201 has, a transmission port, port Tx2, and a reception port, port Rx2, are assigned for serial communication with the peripheral device control board 30. That is, the sub-SoC 201 of the peripheral device control board 20 and a sub-SoC 301, which will be described later, of the peripheral device control board 30 communicate data using two-wire asynchronous serial communication.

[0025] Instead of the sub-SoC 201, a computing device such as a microcomputer may be used.

[0026] The input side of the IC circuit 211 is connected to the terminal T2 of the changeover switch 291, and the output side is connected to the port Rx of the sub-SoC 201. The IC circuit 211 buffers signals received from the main SoC 101, cuts noise, and so on.

[0027] The switching element 212 is driven by the output of the port Tx of the sub-SoC 201 and has an open-drain or open-collector output type. For example, if the switching element 212 is a FET, it has an open-drain output type, and if the switching element 212 is a transistor, it has an open-collector output type. The output terminal (drain or collector) of the switching element 212 is connected to the terminal T2 of the changeover switch 292.

[0028] The connector 221 is a receiving connector for inputting a signal received at the port Rx of the sub-SoC 201 from the main control board 10 in serial communication between the main SoC 101 and the sub-SoC 201. The connector 221 is also connected to the terminal T1 of the changeover switch 291. The connector 221 is connected to the connector 121 of the main control board 10 by a communication line.

[0029] The connector 222 is a transmitting connector for outputting a signal transmitted from the port Tx of the sub-SoC 201 from the peripheral device control board 20 in serial communication between the main SoC 101 and the sub-SoC 201. The connector 222 is also connected to the terminal T1 of the changeover switch 292. The connector 222 is connected to the connector 122 of the main body control board 10 by a communication line.

[0030] The connector 231 is a power connector that receives 5V power from the main body control board 10 and forms the power supply 270. The connector 231 is connected to the connector 131 of the main body control board 10 by a power line.

[0031] The connector 232 is a connector for FG (frame ground), and is connected to the connector 132 of the main body control board 10 by an FG line.

[0032] The fuse 272 is a power supply cutoff means for protecting the circuit when an overcurrent occurs due to a short circuit caused by a foreign object or the like on the peripheral device control board 20, and is a component that forms the power supply 271 ("+5V_F") that ensures circuit protection based on the power supply 270. The fuse 272 melts down when a short circuit caused by a foreign object or the like occurs on the peripheral device control board 20, thereby protecting the circuit of the peripheral device control board 20. Note that instead of the fuse 272, a polyswitch having a similar function may also be used.

[0033] The power supply 270 is formed by a 5V power supply supplied from the main body control board 10. The power supply 270 forms a power supply 271 via a fuse 272.

[0034] The power supply 271 is a 5V power supply for supplying power to each device on the peripheral device control board 20. Therefore, when the fuse 272 blows, the power supply from the power supply 271 stops, causing the sub-SoC 201 to stop operating and making serial communication with the main SoC 101 impossible.

[0035] The switching element 241 is driven by the output of port Tx2 of the sub-SoC 201 and has an open-drain or open-collector output format. For example, if the switching element 241 is a FET, it has an open-drain output format, and if the switching element 241 is a transistor, it has an open-collector output format. The output terminal (drain or collector) of the switching element 241 is connected to the connector 251. Furthermore, the switching element 241 supports partial power down, and there is no problem even if a voltage is applied to the input and output even when power is not being supplied from the power supply 271.

[0036] The input side of the IC circuit 242 is connected to the connector 252, and the output side is connected to the port Rx2 of the sub-SoC 201, and the IC circuit performs buffering and noise reduction of the signal received from the sub-SoC 301 described later. The IC circuit 242 also supports partial power down, and there is no problem in applying a voltage to the input and output even when power is not being supplied from the power supply 271.

[0037] The connector 251 is a transmitting connector for outputting a signal transmitted from port Tx2 of the sub SoC 201 from the peripheral device control board 20 in serial communication between the sub SoC 201 and the sub SoC 301. The connector 251 is connected to a connector 321 (described later) of the peripheral device control board 30 by a communication line.

[0038] The connector 252 is a receiving connector for inputting a signal received at port Rx2 of the sub SoC 201 from the peripheral device control board 30 in serial communication between the sub SoC 201 and the sub SoC 301. The connector 252 is connected to a connector 322 (described later) of the peripheral device control board 30 by a communication line.

[0039] The connector 261 is a power connector for supplying power to the peripheral device control board 30 from a power supply 270, which is a 5V power supply in the peripheral device control board 20. The connector 261 is connected to a connector 331 (described later) of the peripheral device control board 30 by a power line.

[0040] The connector 262 is a connector for FG (frame ground), and is connected to a connector 332 (described later) of the peripheral device control board 30 by an FG line.

[0041] The detection circuit 290 is a circuit for detecting that the fuse 272 has blown due to a short circuit or the like caused by a foreign object or the like on the peripheral device control board 20. The detection circuit 290 has a transistor 290a and a resistor R4. The transistor 290a has a common emitter, a collector connected to one end of the resistor R4, and a base connected to the power supply 271. The resistor R4 has one end connected to the collector of the transistor 290a and the other end connected to the power supply 270. The connection point between one end of the resistor R4 and the collector of the transistor 290a is connected to the input ports of the changeover switches 291 and 292 by a connection line blown_fuse.

[0042] In this case, if fuse 272 is not blown, power supply from power supply 271 is valid, so transistor 290a is on, and connection line blown_fuse is low. On the other hand, if fuse 272 is blown, transistor 290a is not driven by power supply 271 and is off, so connection line blown_fuse is high. That is, when detection circuit 290 detects that fuse 272 has blown, it inverts the signal level of connection line blown_fuse from low to high. Therefore, because connection line blown_fuse is connected to the input ports of selector switches 291 and 292 as described above, selector switches 291 and 292 switch their contacts in accordance with the detection result of detection circuit 290 that fuse 272 has been blown, i.e., the signal level of connection line blown_fuse, as will be described later.

[0043] The circuit of the detection circuit 290 shown in FIG. 1 is an example, and any circuit may be used as long as it can realize the above-described functions.

[0044] Resistor R2 is a pull-up resistor for pulling up the receive line of port Rx of sub-SoC201 with a 5V power supply based on power supply 271.

[0045] Resistor R3 is a pull-up resistor for pulling up the receive line of port Rx2 of sub-SoC201 with a 5V power supply based on power supply 271.

[0046] In this case, even if the power supply of the sub-SoC 201 is not 5V, for example, communication can be performed by converting the voltage level.

[0047] The changeover switch 291 is an electronic component that switches contacts so that a signal transmitted from the main SoC 101 via the connector 221 is received by the port Rx of the sub-SoC 201 or is transmitted to the communication line Tx_thr, bypassing the sub-SoC 201. As shown in FIG. 1 , the changeover switch 291 has terminals T1 to T3. The terminal T1 is connected to the connector 221, the terminal T2 is connected to the input side of the IC circuit 211, and the terminal T3 is connected to the communication line Tx_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 291 determines that the fuse 272 is not blown and switches the contacts so that the terminals T1 and T2 are connected. When the signal level of the connection line blown_fuse connected to the input side is high, the changeover switch 291 determines that the fuse 272 is blown and switches the contacts so that the terminals T1 and T3 are connected.

[0048] The changeover switch 292 is an electronic component that switches contacts to transmit a signal transmitted from the sub-SoC 201 via the connector 222 to the main SoC 101, or to transmit a signal that has passed through the communication line Rx_thr and bypassed the sub-SoC 201 to the main SoC 101 via the connector 222. As shown in FIG. 1 , the changeover switch 292 has terminals T1 to T3. The terminal T1 is connected to the connector 222, the terminal T2 is connected to the output side of the switching element 212, and the terminal T3 is connected to the communication line Rx_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 292 determines that the fuse 272 is not blown and switches the contacts so that the terminals T1 and T2 are connected. When the signal level of the connection line blown_fuse connected to the input side is high, the changeover switch 292 determines that the fuse 272 is blown and switches the contacts so that the terminals T1 and T3 are connected. Hereinafter, the signal indicated by the signal level of the connection line blown_fuse may be referred to as a detection signal.

[0049] 1, the peripheral device control board 30 includes a sub-SoC 301, an IC circuit 311, a switching element 312, a connector 321, a connector 322, a connector 331, a connector 332, a fuse 372, and a resistor R5. Note that the peripheral device control board 30 may be equipped with other components in addition to the components shown in FIG.

[0050] The sub-SoC 301 is a computing device that controls the entire peripheral device control board 30. The sub-SoC 301 operates by receiving power from a power supply 371, which will be described later. Of the input / output ports that the sub-SoC 301 has, a port Tx, which is a transmission port, and a port Rx, which is a reception port, are assigned to perform serial communication with the peripheral device control board 20. In other words, the sub-SoC 301 and the sub-SoC 201 of the peripheral device control board 20 perform data communication via two-wire asynchronous serial communication.

[0051] Instead of the sub-SoC 301, a computing device such as a microcomputer may be used.

[0052] The input side of the IC circuit 311 is connected to the connector 321, and the output side is connected to the port Rx of the sub-SoC 301, and the IC circuit 311 performs buffering and noise reduction of the signal received from the sub-SoC 201, etc.

[0053] The switching element 312 is driven by the output of port Tx of the sub-SoC 301 and has an open-drain or open-collector output format. For example, if the switching element 312 is a FET, it has an open-drain output format, and if the switching element 312 is a transistor, it has an open-collector output format. The output terminal (drain or collector) of the switching element 312 is connected to the connector 322.

[0054] The connector 321 is a receiving connector for inputting a signal received at the port Rx of the sub SoC 301 from the peripheral device control board 20 in serial communication between the sub SoC 201 and the sub SoC 301. The connector 321 is connected to the connector 251 of the peripheral device control board 20 by a communication line.

[0055] The connector 322 is a transmitting connector for outputting a signal transmitted from the port Tx of the sub SoC 301 from the peripheral device control board 30 in serial communication between the sub SoC 201 and the sub SoC 301. The connector 322 is connected to the connector 252 of the peripheral device control board 20 by a communication line.

[0056] The connector 331 is a power connector that receives 5V power from the peripheral device control board 20 and forms the power supply 370. The connector 331 is connected to the connector 261 of the peripheral device control board 20 by a power line.

[0057] The connector 332 is a connector for FG (frame ground), and is connected to the connector 262 of the peripheral device control board 20 by an FG line.

[0058] The fuse 372 is a power supply cutoff means for circuit protection when an overcurrent occurs due to a short circuit caused by a foreign object or the like on the peripheral device control board 30, and is a component that forms the power supply 371 ("+5V_F") that ensures circuit protection based on the power supply 370. The fuse 372 melts down when a short circuit caused by a foreign object or the like occurs on the peripheral device control board 30, thereby protecting the circuit of the peripheral device control board 30. Note that a polyswitch having a similar function may be used instead of the fuse 372.

[0059] The power supply 370 is formed by a 5V power supply supplied from the peripheral device control board 20. The power supply 370 forms a power supply 371 via a fuse 372.

[0060] Power supply 371 is a 5V power supply for supplying power to each device on peripheral device control board 30. Therefore, when fuse 372 blows, power supply from power supply 371 stops, so that sub-SoC 301 stops operating and serial communication with sub-SoC 201 becomes impossible.

[0061] Resistor R5 is a pull-up resistor for pulling up the receive line of port Rx of sub-SoC 301 with a 5V power supply based on power supply 371. In this case, even if the power supply of sub-SoC 301 is not 5V, for example, communication can be performed by converting the voltage level.

[0062] The connectors connecting the main body control board 10, the peripheral device control board 20, and the peripheral device control board 30 may be connected by, for example, a harness or an FFC (flexible flat cable). The main SoC 101, the sub SoC 201, and the sub SoC 301 correspond to the "first control device," the "second control device," and the "third control device," respectively, of the present invention. The fuse 272 corresponds to the "interrupter" of the present invention, and the detection circuit 290 corresponds to the "detection device" of the present invention.

[0063] (Overview of electronic device operation) Fig. 2 is a diagram showing a circuit configuration of the electronic device in a normal state according to the embodiment. Fig. 3 is a diagram showing a circuit configuration of the electronic device in a state where a fuse of the electronic device according to the embodiment is blown. Fig. 4 is a timing chart showing an example of a communication operation between a main body control board and a peripheral device control board of the electronic device according to the embodiment. An overview of the operation of the electronic device 1 according to the present embodiment will be described with reference to Figs. 2 to 4.

[0064] First, assume that the configuration of electronic device 1 shown in FIG. 1 does not include changeover switches 291 and 292, i.e., connector 221 is directly connected to the input side of IC circuit 211, and connector 222 is directly connected to the output side of switching element 212. In this case, if fuse 272 blows, even if peripheral device control board 30 is normal and operating normally, operation of sub-SoC 201 will stop, and main SoC 101 will be unable to communicate with sub-SoC 301, which is located downstream of sub-SoC 201. Therefore, electronic device 1 according to this embodiment is equipped with changeover switches 291 and 292, as described above with reference to FIG. 1. The operation of electronic device 1 will be described in detail below.

[0065] In a normal state where the fuse 272 is not blown, the detection signal from the detection circuit 290 is at a low level, and therefore the changeover switches 291 and 292 switch their contacts so that the terminals T1 and T2 are connected, as shown in Fig. 2. As a result, the power supply 271 has the same voltage as the power supply 270, as shown in Fig. 4(a), and the connector 221 is connected to the input side of the IC circuit 211, and the connector 222 is connected to the output side of the switching element 212. As a result, as shown in Fig. 4(a), data communication is performed between the port Tx and port Rx of the main SoC 101 and the port Rx and port Tx of the sub SoC 201, respectively, and between the port Tx2 and port Rx2 of the sub SoC 201 and the port Rx and port Tx of the sub SoC 301, respectively. That is, when the main SoC 101 of the main body control board 10 communicates data with the sub-SoC 301 of the peripheral device control board 30 , the data communication is performed via the sub-SoC 201 of the peripheral device control board 20 .

[0066] On the other hand, when the fuse 272 is blown, the detection signal from the detection circuit 290 is at a high level, and therefore the changeover switches 291 and 292 switch their contacts so that the terminals T1 and T3 are connected, as shown in FIG. 3. As a result, the power supply 271 is cut off from the power supply 270 as shown in FIG. 4(b), the connector 221 is connected to the communication line Tx_thr (i.e., the connector 251), and the connector 222 is connected to the communication line Rx_thr (i.e., the connector 252). As a result, as shown in FIG. 4(b), direct data communication is performed between the ports Tx and Rx of the main SoC 101 and the ports Rx and Tx of the sub-SoC 301, respectively. That is, the main SoC 101 of the main body control board 10 performs direct data communication with the sub-SoC 301 of the peripheral device control board 30 without going through (skipping) the sub-SoC 201 of the peripheral device control board 20. In this way, even if the power supply to the peripheral control board 20 connected in a daisy chain from the main control board 10 is cut off, communication can still be made with the subsequent peripheral control board 30 connected in a daisy chain from the main control board 10.

[0067] (When multiple peripheral control boards are connected) FIG. 5 is a diagram showing a configuration in which peripheral device control boards are connected in multiple stages to a main body control board in a daisy chain connection in an electronic device according to an embodiment.

[0068] 1 to 3, the peripheral control board connected in a daisy chain between the main body control board 10 and the peripheral control board 30 is one peripheral control board 20, but this is not limited to this. That is, as shown in Fig. 5, a configuration may be adopted in which a plurality of (n) peripheral control boards 20_1 to 20_n having the same configuration as the peripheral control board 20 are connected in a daisy chain between the main body control board 10 and the peripheral control board 30. Note that, when referring to any of the peripheral control boards 20_1 to 20_n, it will be simply referred to as the peripheral control board 20.

[0069] In other words, if the peripheral control board 20 in the later stage closer to the peripheral control board 30 is taken as the target board, the target board will receive power from the peripheral control board 20 in the previous stage adjacent to the target board, and the sub-SoC 201 of the target board will communicate with the sub-SoC 201 of the peripheral control board 20 in the previous stage adjacent to the target board.

[0070] Here, the configuration similar to that of the peripheral device control board 20 may be a configuration that uses the same communication method and includes the fuse 272, the selector switches 291 and 292, and the detection circuit 290, but other configurations may be different. Even with the configuration shown in Fig. 5, even if the fuse 272 of any of the peripheral device control boards 20_1 to 20_n is blown, data communication can be continued by skipping that peripheral device control board. Furthermore, whether the peripheral device control boards with blown fuses 272 are consecutive or discontinuous, data communication can be continued between the other control boards by skipping the peripheral device control board with the blown fuse 272.

[0071] As shown in FIG. 5, in the case of an image forming apparatus, an electronic device 1 including a plurality of peripheral control boards 20_1 to 20_n includes units having different functions such as a finisher or a stacker.

[0072] (Main SoC operation flow) Fig. 6 is a flowchart showing an example of the operation flow of the main SoC of the electronic device according to the embodiment. The operation flow of the main SoC 101 of the electronic device 1 according to the present embodiment will be described with reference to Fig. 6. Note that in Fig. 6, when referring to the peripheral control board 20, the peripheral control board 30, and any of the peripheral control boards 20_1 to 20_n shown in Fig. 5 with which the main SoC 101 of the main body control board 10 communicates, they will be described as "peripheral control boards."

[0073] <Step S101> First, the power supply of the electronic device 1 is turned on, and the process proceeds to step S102.

[0074] <Step S102> The main SoC 101 of the main body control board 10 starts data communication with the peripheral device control boards connected in a daisy chain, and then the process proceeds to step S103.

[0075] <Step S103> In data communication, the main SoC 101 acquires the identification ID of each device having a peripheral control board as a communication destination, and stores the ID in an internal non-volatile memory (storage means). Note that the device identification ID may be information other than the device ID that indicates the type of device, etc. Then, the process proceeds to step S104.

[0076] <Step S104> The main SoC 101 determines whether the identification IDs of the devices having the peripheral control boards with which data communication was performed at the previous startup are stored in the non-volatile memory. If the identification IDs are stored (step S104: Yes), the process proceeds to step S105. If the identification IDs are not stored (step S104: No), the process ends because this is the initial startup of the electronic device 1 after installation.

[0077] <Step S105> Furthermore, the main SoC 101 determines whether the identification IDs of the devices having the peripheral control boards with which data communication was performed at the previous startup do not match the identification IDs acquired at step S103. If they do not match (step S105: Yes), the process proceeds to step S106. If they match (step S105: No), the flow ends because there is no change in the daisy-chain connection configuration of the electronic device 1 at the previous startup.

[0078] <Step S106> If the identification IDs do not match, the main SoC 101 detects that a fuse in one of the peripheral control boards with which data communication was performed at the previous startup may have been blown. In addition to a blown fuse, a mismatch in the identification IDs may also be caused by a malfunction of the device or by the user intentionally removing the device. Therefore, the main SoC 101 may notify the electronic device 1 by displaying the detection result on a display device or by sending an email that a fuse in one of the peripheral control boards with which data communication was performed at the previous startup may have been blown. This makes it easy to determine whether the device has a blown fuse, is malfunctioning, or was intentionally removed.

[0079] As described above, in the electronic device according to this embodiment, the peripheral control board 20 receives power from the main body control board 10, the peripheral control board 30 receives power from the peripheral control board 20, the main SoC 101 is mounted on the main body control board 10 and controls the operation of the main body control board 10, the sub-SoC 201 is mounted on the peripheral control board 20 and controls the operation of the peripheral control board 20 and communicates with the main SoC 101, the sub-SoC 301 is mounted on the peripheral control board 30 and controls the operation of the peripheral control board 30 and communicates with the sub-SoC 201, and the fuse 272 is provided on the peripheral control board 20. When an overcurrent occurs in the peripheral control board 20, the power supply from the main control board 10 is cut off, a detection circuit 290 is provided on the peripheral control board 20 and detects that the power has been cut off by the fuse 272, and changeover switches 291 and 292 are provided on the peripheral control board 20 and switch between a communication path between the main SoC 101 and the sub SoC 201 and a communication path between the main SoC 101 and the sub SoC 301, and when the detection circuit 290 detects that the power has been cut off by the fuse 272, the changeover switches 291 and 292 switch to the communication path between the main SoC 101 and the sub SoC 301. As a result, even when the power supply from the main control board 10 to the peripheral control board 20 connected in a daisy chain is cut off, the main control board 10 can communicate with the subsequent peripheral control board 30 connected in a daisy chain.

[0080] (Variation 1) The electronic device according to this modification will be described, focusing on the differences from the electronic device 1 according to the above-described embodiment. In the above-described embodiment, the configuration was described for the case where the communication method is UART serial communication. In this modification, the configuration will be described for the case where the communication method is SPI (Serial Peripheral Interface) serial communication.

[0081] Fig. 7 is a diagram showing an example of the circuit configuration of the main body control board and peripheral device control board of the electronic device according to Modification 1. With reference to Fig. 7, the circuit configuration of the main body control board 10a and peripheral device control boards 20a and 30a of the electronic device 1a according to this modification will be described.

[0082] In the electronic device 1a shown in Figure 7, a main body control board 10a is connected in series to a peripheral device control board 20a and a peripheral device control board 30a in a daisy chain, and data is communicated between them using SPI three-wire serial communication. In this SPI serial communication, data is communicated using three communication lines: a clock (SCK), a serial output (SO), and a serial input (SI). The main body control board 10a, the peripheral device control board 20a, and the peripheral device control board 30a correspond to the "first board," the "second board," and the "third board" of the present invention, respectively.

[0083] 7, the main body control board 10a includes a main SoC 101a, a connector 121a, a connector 122a, a connector 123a, a connector 131, and a connector 132. The connectors 131, 132, and the power supply 140 are the same as those in the above-described embodiment.

[0084] The main SoC 101a is a computing device that controls the entire main body control board 10a. The main SoC 101a operates by receiving power from a power supply 140. Among the ports possessed by the main SoC 101a, port SCK for transmitting a clock signal, port SO which is a transmission port, and port SI which is a reception port are assigned to perform serial communication with the peripheral device control board 20a. In other words, the main SoC 101a of the main body control board 10a and the sub-SoC 201a (described later) perform data communication via three-wire synchronous serial communication.

[0085] The connector 121a is a transmitting connector for outputting a clock signal transmitted from the port SCK of the main SoC 101a from the main control board 10a in serial communication between the main SoC 101a and the sub-SoC 201a. The connector 121a is connected to a connector 221a (described later) of the peripheral device control board 20a by a communication line.

[0086] The connector 122a is a transmission connector for outputting a signal transmitted from the port SO of the main SoC 101a from the main control board 10a in serial communication between the main SoC 101a and the sub-SoC 201a. The connector 122a is connected to a connector 222a (described later) of the peripheral device control board 20a by a communication line.

[0087] The connector 123a is a receiving connector for inputting a signal received at a port SI of the main SoC 101a from the peripheral device control board 20a in serial communication between the main SoC 101a and the sub-SoC 201a. The connector 123a is connected to a connector 223a (described later) of the peripheral device control board 20a by a communication line.

[0088] 7, the peripheral device control board 20a includes a sub-SoC 201a, connectors 221a, 222a, 223a, connectors 231, 232, IC circuits 241a, 242a, 243a, connectors 251a, 252a, 253a, fuses 272, connectors 261, 262, a detection circuit 290, and selector switches 291a, 292a, and 293a. Note that the connectors 231, 232, fuses 272, connectors 261, 262, detection circuit 290, power supplies 270, and 271 are the same as those in the above-described embodiment. The selector switches 291a to 293a correspond to the "switching means" of the present invention.

[0089] The sub-SoC 201a is a computing device that controls the entire peripheral device control board 20a. The sub-SoC 201a operates by receiving power from the power supply 271. Among the input / output ports of the sub-SoC 201a, port SCK for receiving a clock signal, port SO as a transmission port, and port SI as a reception port are assigned for serial communication with the main body control board 10a. That is, the main SoC 101a of the main body control board 10a and the sub-SoC 201a perform data communication via three-wire synchronous serial communication. Among the input / output ports of the sub-SoC 201a, port SCK for transmitting a clock signal, port SO2 as a transmission port, and port SI2 as a reception port are assigned for serial communication with the peripheral device control board 30a. That is, the sub-SoC 201a of the peripheral device control board 20a and a sub-SoC 301a (described later) of the peripheral device control board 30a perform data communication via three-wire synchronous serial communication.

[0090] The connector 221a is a receiving connector for inputting a clock signal received at the port SCK of the sub-SoC 201a from the main control board 10a in serial communication between the main SoC 101a and the sub-SoC 201a. The connector 221a is also connected to the terminal T1 of the changeover switch 291a. The connector 221a is connected to the connector 121a of the main control board 10a via a communication line.

[0091] The connector 222a is a receiving connector for inputting a signal received at port SI of the sub-SoC 201a from the main control board 10a in serial communication between the main SoC 101a and the sub-SoC 201a. The connector 222a is also connected to terminal T1 of the changeover switch 292a. The connector 222a is connected to the connector 122a of the main control board 10a via a communication line.

[0092] The connector 223a is a transmitting connector for outputting a signal transmitted from the port SO of the sub-SoC 201a from the peripheral device control board 20a in serial communication between the main SoC 101a and the sub-SoC 201a. The connector 223a is also connected to the terminal T1 of the changeover switch 293a. The connector 223a is connected to the connector 123a of the main body control board 10a via a communication line.

[0093] The input side of the IC circuit 241a is connected to the port SCK2 of the sub-SoC 201a, and the output side is connected to the connector 251a, and the IC circuit 241a is an IC circuit for processing the clock signal output from the port SCK2 of the sub-SoC 201a.

[0094] The input side of the IC circuit 242a is connected to the port SO2 of the sub-SoC 201a, and the output side is connected to the connector 252a, and the IC circuit 242a is an IC circuit for processing signals output from the port SO2 of the sub-SoC 201a.

[0095] The input side of the IC circuit 243a is connected to the connector 253a, and the output side is connected to the port SI2 of the sub-SoC 201a, and the IC circuit 243a performs buffering and noise reduction of the signal received from the sub-SoC 301a.

[0096] The connector 251a is a transmitting connector for outputting a clock signal transmitted from the port SCK2 of the sub-SoC 201a from the peripheral device control board 30a in serial communication between the sub-SoC 201a and the sub-SoC 301a. The connector 251a is connected to a connector 321a (described later) of the peripheral device control board 30a by a communication line.

[0097] The connector 252a is a transmitting connector for outputting a signal transmitted from the port SO2 of the sub-SoC 201a from the peripheral device control board 30a in serial communication between the sub-SoC 201a and the sub-SoC 301a. The connector 252a is connected to a connector 322a (described later) of the peripheral device control board 30a by a communication line.

[0098] The connector 253a is a receiving connector for inputting a signal received at port SI2 of the sub-SoC 201a from the peripheral device control board 30a in serial communication between the sub-SoC 201a and the sub-SoC 301a. The connector 253a is connected to a connector 323a (described later) of the peripheral device control board 30a by a communication line.

[0099] The changeover switch 291a is an electronic component that switches contacts so that the clock signal transmitted from the main SoC 101a via the connector 221a is received by the port SCK of the sub SoC 201a, or is transmitted to the communication line SCK_thr, skipping the sub SoC 201a. As shown in FIG. 7, the changeover switch 291a has terminals T1 to T3. The terminal T1 is connected to the connector 221a, the terminal T2 is connected to the port SCK of the sub SoC 201a, and the terminal T3 is connected to the communication line SCK_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 291a determines that the fuse 272 is not blown and switches the contacts so that the terminals T1 and T2 are connected. Furthermore, when the signal level of the connection line blown_fuse connected to the input side is at a high level, the changeover switch 291a determines that the fuse 272 is blown and switches the contacts so that the terminal T1 and the vertex T3 are connected.

[0100] The changeover switch 292a is an electronic component that switches contacts so that a signal transmitted from the main SoC 101a via the connector 222a is received by the port SI of the sub-SoC 201a or transmitted to the communication line SO_thr, bypassing the sub-SoC 201a. As shown in FIG. 7, the changeover switch 292a has terminals T1 to T3. Terminal T1 is connected to the connector 222a, terminal T2 is connected to the port SI of the sub-SoC 201a, and terminal T3 is connected to the communication line SO_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 292a determines that the fuse 272 is not blown and switches the contacts so that terminal T1 and terminal T2 are connected. When the signal level of the connection line blown_fuse connected to the input side is high, the changeover switch 292a determines that the fuse 272 is blown and switches the contacts so that terminal T1 and terminal T3 are connected.

[0101] The changeover switch 293a is an electronic component that switches contacts to transmit a signal transmitted from the sub-SoC 201a via the connector 223a to the main SoC 101a, or to transmit a signal that has passed through the communication line SI_thr, skipping the sub-SoC 202a, to the main SoC 101a via the connector 223a. As shown in FIG. 7, the changeover switch 293a has terminals T1 to T3. The terminal T1 is connected to the connector 223a, the terminal T2 is connected to the port SO of the sub-SoC 201a, and the terminal T3 is connected to the communication line SI_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 293a determines that the fuse 272 is not blown and switches the contacts so that the terminals T1 and T2 are connected. Furthermore, when the signal level of the connection line blown_fuse connected to the input side is at a high level, the changeover switch 293a determines that the fuse 272 is blown and switches the contacts so that the terminal T1 and the vertex T3 are connected.

[0102] 7, the peripheral device control board 30a includes a sub-SoC 301a, a connector 321a, a connector 322a, a connector 323a, a connector 331, a connector 332, and a fuse 372. The connector 331, the connector 332, the fuse 372, the power supply 370, and the power supply 371 are the same as those in the above-described embodiment.

[0103] The sub-SoC 301a is a computing device that controls the entire peripheral control board 30a. The sub-SoC 301a operates by receiving power from a power supply 371. Among the input / output ports of the sub-SoC 301a, a port SCK for receiving a clock signal, a port SO which is a transmission port, and a port SI which is a reception port are assigned to perform serial communication with the peripheral control board 20a. In other words, the sub-SoC 301a and the sub-SoC 201a of the peripheral control board 20a perform data communication using three-wire synchronous serial communication.

[0104] The connector 321a is a receiving connector for inputting a clock signal received at the port SCK of the sub-SoC 301a from the peripheral device control board 20a in serial communication between the sub-SoC 201a and the sub-SoC 301a. The connector 321a is connected to the connector 251a of the peripheral device control board 20a by a communication line.

[0105] The connector 322a is a receiving connector for inputting a signal received at port SI of the sub-SoC 301a from the peripheral device control board 20a in serial communication between the sub-SoC 201a and the sub-SoC 301a. The connector 322a is connected to the connector 252a of the peripheral device control board 20a by a communication line.

[0106] The connector 323a is a transmitting connector for outputting a signal transmitted from the port SO of the sub-SoC 301a from the peripheral device control board 30a in serial communication between the sub-SoC 201a and the sub-SoC 301a. The connector 323a is connected to the connector 253a of the peripheral device control board 20a by a communication line.

[0107] As described above, the electronic device 1a according to this modification is configured to communicate data with each other using SPI three-wire serial communication. Even in this case, even if the power supply to the peripheral control board 20a connected in a daisy chain from the main body control board 10a is cut off, the main body control board 10a can still communicate with the subsequent peripheral control board 30a connected in a daisy chain.

[0108] 7, the communication method is SPI three-wire serial communication, but it may be SPI four-wire with a chip select (CS) signal added. Also, the main SoC 101a, sub-SoC 201a, and sub-SoC 301a correspond to the "first control device," "second control device," and "third control device" of the present invention, respectively.

[0109] (Variation 2) The electronic device according to this modification will be described, focusing on the differences from the electronic device 1 according to the above embodiment. In this modification, a configuration will be described in which the communication method is I2C (Inter-Integrated Circuit) serial communication.

[0110] Fig. 8 is a diagram showing an example of the circuit configuration of the main body control board and peripheral device control board of the electronic device according to Modification 2. With reference to Fig. 8, the circuit configuration of the main body control board 10b and peripheral device control boards 20b and 30b of the electronic device 1b according to this modification will be described.

[0111] In the electronic device 1b shown in Figure 8, a main body control board 10b is connected in series to a peripheral device control board 20b and a peripheral device control board 30b in a daisy chain connection, and data is communicated between them using two-wire serial communication using the I2C communication method. In this I2C serial communication, data is communicated using two communication lines: a clock (SCL) and a data input / output (SDA). The main body control board 10b, the peripheral device control board 20b, and the peripheral device control board 30b correspond to the "first board," the "second board," and the "third board," respectively, in the present invention.

[0112] 8, the main body control board 10b includes a main SoC 101b, a connector 121b, a connector 122b, a connector 131, and a connector 132. The connectors 131, 132, and the power supply 140 are the same as those in the above-described embodiment.

[0113] The main SoC 101b is a computing device that controls the entire main body control board 10b. The main SoC 101b operates by receiving power from a power supply 140. Among the ports that the main SoC 101b has, port SCL for transmitting a clock signal and port SDA, a transmit / receive port, are assigned to perform serial communication with the peripheral device control board 20b. In other words, the main SoC 101b of the main body control board 10b and the sub-SoC 201b (described later) perform data communication via two-wire synchronous serial communication.

[0114] The connector 121b is a transmission connector for outputting a clock signal transmitted from the port SCL of the main SoC 101b from the main control board 10b in serial communication between the main SoC 101b and the sub-SoC 201b. The connector 121b is connected to a connector 221b (described later) of the peripheral device control board 20b via a communication line.

[0115] The connector 122b is a transmission / reception connector for inputting / outputting signals transmitted / received via the port SDA of the main SoC 101b to / from the main body control board 10b in serial communication between the main SoC 101b and the sub-SoC 201b. The connector 122b is connected to a connector 222b (described later) on the peripheral device control board 20b via a communication line.

[0116] 8, the peripheral device control board 20b includes a sub-SoC 201b, a connector 221b, a connector 222b, a connector 231, a connector 232, an IC circuit 241b, a connector 251b, a connector 252b, a fuse 272, a connector 261, a connector 262, a detection circuit 290, a changeover switch 291b, a changeover switch 292b, a changeover switch 293b, a resistor R2b, and a resistor R3b. Note that the connector 231, the connector 232, the fuse 272, the connector 261, the connector 262, the detection circuit 290, the power supply 270, and the power supply 271 are the same as those in the above-described embodiment. The changeover switches 291b to 293b correspond to the "switching means" of the present invention.

[0117] The sub-SoC 201b is a computing device that controls the entire peripheral device control board 20b. The sub-SoC 201b operates by receiving power from the power supply 271. Among the ports of the sub-SoC 201b, a port SCL for receiving a clock signal and a port SDA, which is a transmission / reception port, are assigned for serial communication with the main body control board 10b. That is, the main SoC 101b of the main body control board 10b and the sub-SoC 201b perform data communication using two-wire synchronous serial communication. Among the ports of the sub-SoC 201b, a port SCL for transmitting a clock signal and a port SDA2, which is a transmission / reception port, are assigned for serial communication with the peripheral device control board 30b. That is, the sub-SoC 201b of the peripheral device control board 20b and a sub-SoC 301b (described later) of the peripheral device control board 30b perform data communication using two-wire synchronous serial communication.

[0118] The connector 221b is a receiving connector for inputting a clock signal received at the port SCL of the sub-SoC 201b from the main control board 10b during serial communication between the main SoC 101b and the sub-SoC 201b. The connector 221b is also connected to the terminal T1 of the changeover switch 291b. The connector 221b is connected to the connector 121b of the main control board 10b via a communication line.

[0119] The connector 222b is a transmission / reception connector for inputting / outputting signals transmitted and received at the port SDA of the sub-SoC 201b from / to the main body control board 10b during serial communication between the main SoC 101b and the sub-SoC 201b. The connector 222b is also connected to the terminal T1 of the changeover switch 292b. The connector 222b is connected to the connector 122b of the main body control board 10b via a communication line.

[0120] The input side of the IC circuit 241b is connected to the port SCL2 of the sub-SoC 201b, and the output side is connected to the connector 251b, and the IC circuit 241b is an IC circuit for processing the clock signal output from the port SCL2 of the sub-SoC 201b.

[0121] The connector 251b is a transmission connector for outputting a clock signal transmitted from the port SCL2 of the sub-SoC 201b from the peripheral device control board 20b in serial communication between the sub-SoC 201b and the sub-SoC 301b. The connector 251b is connected to a connector 321b (described later) of the peripheral device control board 30b by a communication line.

[0122] The connector 252b is a transmission / reception connector for inputting / outputting signals transmitted / received at the port SDA2 of the sub-SoC 201b from / to the peripheral device control board 20b in serial communication between the sub-SoC 201b and the sub-SoC 301b. The connector 252b is connected to a connector 322b (described later) of the peripheral device control board 30b by a communication line.

[0123] Resistor R2b is a pull-up resistor for pulling up the receive line of port SCL of sub-SoC201b with a 5V power supply based on power supply 271.

[0124] The resistor R3b is a pull-up resistor for pulling up the transmit / receive line of the port SDA of the sub-SoC 201b with a 5V power supply based on the power supply 271.

[0125] The changeover switch 291b is an electronic component that switches contacts so that the clock signal transmitted from the main SoC 101b via the connector 221b is received by the port SCL of the sub SoC 201b, or is transmitted to the communication line SCL_thr, bypassing the sub SoC 201b. As shown in FIG. 8, the changeover switch 291b has terminals T1 to T3. The terminal T1 is connected to the connector 221b, the terminal T2 is connected to the port SCL of the sub SoC 201b, and the terminal T3 is connected to the communication line SCL_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 291b determines that the fuse 272 is not blown and switches the contacts so that the terminals T1 and T2 are connected. Furthermore, when the signal level of the connection line blown_fuse connected to the input side is at a high level, the changeover switch 291b determines that the fuse 272 is blown and switches the contacts so that the terminal T1 and the vertex T3 are connected.

[0126] The changeover switch 292b is an electronic component that switches contacts so that signals transmitted from and received by the main SoC 101b via the connector 222b are transmitted to and received by the port SDA of the sub SoC 201b, or are transmitted and received by and received by the communication line SDA_thr, bypassing the sub SoC 201b. As shown in FIG. 8, the changeover switch 292b has terminals T1 to T3. The terminal T1 is connected to the connector 222b, the terminal T2 is connected to the port SDA of the sub SoC 201b, and the terminal T3 is connected to the communication line SDA_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 292b determines that the fuse 272 is not blown and switches the contacts so that the terminals T1 and T2 are connected. Furthermore, when the signal level of the connection line blown_fuse connected to the input side is at a high level, the changeover switch 292b switches the contacts so that the terminal T1 and the vertex T3 are connected, assuming that the fuse 272 is blown.

[0127] The changeover switch 293b is an electronic component that switches contacts to transmit signals transmitted from and received by the sub-SoC 201b via the connector 252b to and from the sub-SoC 301b, or to transmit signals that have passed through the communication line SDA_thr, bypassing the sub-SoC 201b, to and from the sub-SoC 301b via the connector 252b. As shown in FIG. 8, the changeover switch 293b has terminals T1 to T3. The terminal T1 is connected to the connector 252b, the terminal T2 is connected to the port SDA2 of the sub-SoC 201b, and the terminal T3 is connected to the communication line SDA_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 293b determines that the fuse 272 is not blown and switches the contacts so that the terminals T1 and T2 are connected. Furthermore, when the signal level of the connection line blown_fuse connected to the input side is high, the selector switch 293b switches its contacts to connect the terminal T1 and the node T3, assuming that the fuse 272 is blown. The signal at port SDA2 of the sub-SoC 201b is a bidirectional signal, and it is not suitable to configure it using an output element such as a buffer. Furthermore, when the fuse 272 is blown, the power to the sub-SoC 201b is not supplied, and voltage is applied from the communication line of port SDA2, which can cause the sub-SoC 201b to malfunction. Furthermore, since the fuse 272 is blown, there is no problem if the peripheral device control board 20b itself is determined to be faulty and replaced. However, if repair is performed by replacing only the blown fuse 272, the application of voltage to the unpowered sub-SoC 201b becomes a problem. Therefore, by providing a changeover switch 293b on the output side of port SDA2 as well, even if the fuse 272 is blown, communication between the main SoC 101b and the sub SoC 301b is possible without applying voltage.

[0128] 8, the peripheral device control board 30b includes a sub-SoC 301b, a connector 321b, a connector 322b, a connector 331, a connector 332, a fuse 372, a resistor R5b, and a resistor R6b. The connector 331, the connector 332, the fuse 372, the power supply 370, and the power supply 371 are the same as those in the above-described embodiment.

[0129] The sub-SoC 301b is a computing device that controls the entire peripheral control board 30b. The sub-SoC 301b operates by receiving power from a power supply 371. Of the input / output ports that the sub-SoC 301b has, a port SCL, which is a receiving port, and a port SDA, which is a transmitting / receiving port, are assigned to perform serial communication with the peripheral control board 20b. In other words, the sub-SoC 301b and the sub-SoC 201b of the peripheral control board 20b perform data communication using two-wire synchronous serial communication.

[0130] The connector 321b is a receiving connector for inputting a clock signal received at the port SCL of the sub-SoC 301b from the peripheral device control board 20b in serial communication between the sub-SoC 201b and the sub-SoC 301b. The connector 321b is connected to the connector 251b of the peripheral device control board 20b by a communication line.

[0131] The connector 322b is a transmission / reception connector for inputting / outputting signals transmitted / received from the port SDA of the sub-SoC 301b to / from the peripheral device control board 30b in serial communication between the sub-SoC 201b and the sub-SoC 301b. The connector 322b is connected to the connector 252b of the peripheral device control board 20b by a communication line.

[0132] Resistor R5b is a pull-up resistor for pulling up the receive line of port SCL of sub-SoC301b with a 5V power supply based on power supply 371.

[0133] Resistor R6b is a pull-up resistor for pulling up the transmit / receive line of port SDA of sub-SoC 301b with a 5V power supply based on power supply 371.

[0134] As described above, electronic device 1b according to this modification is configured to communicate data with each other using two-wire serial communication based on I2C. Even in this case, even if the power supply to peripheral control board 20b connected in a daisy chain from main body control board 10b is cut off, main body control board 10b can still communicate with subsequent peripheral control board 30b connected in a daisy chain.

[0135] Furthermore, the main SoC 101b, the sub-SoC 201b, and the sub-SoC 301b correspond to the "first control device," the "second control device," and the "third control device," respectively, of the present invention.

[0136] (Variation 3) The electronic device according to this modification will be described, focusing on the differences from the electronic device 1 according to the above-described embodiment. In this modification, a configuration will be described for a case where a differential signal is used as a communication method, for example, serial communication by USB (Universal Serial Bus).

[0137] 9 is a diagram showing an example of the circuit configuration of a main body control board and a peripheral device control board of an electronic device according to Modification 3. The circuit configuration of a main body control board 10c and peripheral device control boards 20c and 30c of an electronic device 1c according to this modification will be described with reference to FIG. 9. Note that, in addition to USB, serial communication using differential signals can also be applied to HDMI (registered trademark) (High-Definition Multimedia Interface), SATA (Serial Advanced Technology Attachment), Ethernet (registered trademark), LVDS (Low Voltage Differential Signaling), and the like. The following description will be given assuming serial communication via USB.

[0138] In the electronic device 1c shown in Figure 9, a main body control board 10c is connected in series to a peripheral device control board 20c and a peripheral device control board 30c in a daisy chain, and data is communicated between them via USB serial communication using differential signals as the communication method. In this USB serial communication, data is communicated using two signal lines (D+, D-) for transmitting and receiving differential signals. The main body control board 10c, the peripheral device control board 20c, and the peripheral device control board 30c correspond to the "first board," "second board," and "third board" of the present invention, respectively.

[0139] 9, the main body control board 10c includes a main SoC 101c, a connector 121c, a connector 122c, a connector 131, and a connector 132. The connectors 131, 132, and the power supply 140 are the same as those in the above-described embodiment.

[0140] The main SoC 101c is a computing device that controls the entire main body control board 10c. The main SoC 101c operates by receiving power from a power supply 140. Among the ports possessed by the main SoC 101c, port D+ and port D- are assigned for transmitting and receiving differential signals to perform serial communication with the peripheral device control board 20c. In other words, the main SoC 101c of the main body control board 10c and the sub-SoC 201c (described later) perform data communication via USB serial communication using differential signals.

[0141] The connector 121c is a transmission / reception connector for inputting / outputting signals transmitted / received from port D+ of the main SoC 101c to / from the main body control board 10c in serial communication between the main SoC 101c and the sub SoC 201c. The connector 121c is connected to a connector 221c (described later) of the peripheral device control board 20c by a communication line.

[0142] The connector 122c is a transmission / reception connector for inputting / outputting signals transmitted / received from port D+ of the main SoC 101c to / from the main body control board 10c in serial communication between the main SoC 101c and the sub SoC 201c. The connector 122c is connected to a connector 222c (described later) of the peripheral device control board 20c by a communication line.

[0143] 9, the peripheral device control board 20c includes a sub-SoC 201c, a connector 221c, a connector 222c, a connector 231, a connector 232, a connector 251c, a connector 252c, a fuse 272, a connector 261, a connector 262, a detection circuit 290, a changeover switch 291c, a changeover switch 292c, a changeover switch 293c, and a changeover switch 294c. The connectors 231, 232, the fuse 272, the connectors 261, 262, the detection circuit 290, the power supplies 270, and the power supplies 271 are the same as those in the above-described embodiment. The changeover switches 291c to 294c correspond to the "switching means" of the present invention.

[0144] The sub-SoC 201c is a computing device that controls the entire peripheral control board 20c. The sub-SoC 201c operates by receiving power from the power supply 271. Among the ports of the sub-SoC 201c, ports D+ and D- are assigned for transmitting and receiving differential signals to perform serial communication with the main body control board 10c. That is, the main SoC 101c of the main body control board 10c and the sub-SoC 201c perform data communication via USB serial communication using differential signals. Furthermore, among the ports of the sub-SoC 201c, ports D2+ and D2- are assigned for transmitting and receiving differential signals to perform serial communication with the peripheral control board 30c. That is, the sub-SoC 201c of the peripheral control board 20c and a sub-SoC 301c (described later) of the peripheral control board 30c perform data communication via USB serial communication using differential signals.

[0145] The connector 221c is a transmission / reception connector for inputting and outputting signals transmitted and received at port D+ of the sub-SoC 201c from the main control board 10c during serial communication between the main SoC 101c and the sub-SoC 201c. The connector 221c is also connected to terminal T1 of the changeover switch 291c. The connector 221c is connected to the connector 121c of the main control board 10c via a communication line.

[0146] The connector 222c is a transmission / reception connector for inputting / outputting signals transmitted and received at port D- of the sub-SoC 201c from / to the main body control board 10c during serial communication between the main SoC 101c and the sub-SoC 201c. The connector 222c is also connected to terminal T1 of the changeover switch 292c. The connector 222c is connected to the connector 122c of the main body control board 10c by a communication line.

[0147] The connector 251c is a transmission / reception connector for inputting / outputting signals transmitted / received from port D2+ of the sub-SoC 201c to / from the peripheral device control board 20c during serial communication between the sub-SoC 201c and the sub-SoC 301c. The connector 251c is also connected to terminal T1 of the changeover switch 293c. The connector 251c is connected to a connector 321c (described later) of the peripheral device control board 30c via a communication line.

[0148] The connector 252c is a transmission / reception connector for inputting / outputting signals transmitted / received from port D2 of the sub-SoC 201c to / from the peripheral device control board 20c during serial communication between the sub-SoC 201c and the sub-SoC 301c. The connector 252c is also connected to terminal T1 of the changeover switch 294c. The connector 252c is connected to a connector 322c (described later) of the peripheral device control board 30c via a communication line.

[0149] The changeover switch 291c is an electronic component that switches contacts so that signals transmitted and received by the main SoC 101c via the connector 221c are transmitted and received at the port D+ of the sub SoC 201c, or are transmitted and received at the communication line D+_thr, bypassing the sub SoC 201c. As shown in FIG. 9, the changeover switch 291c has terminals T1 to T3. The terminal T1 is connected to the connector 221c, the terminal T2 is connected to the port D+ of the sub SoC 201c, and the terminal T3 is connected to the communication line D+_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 291c determines that the fuse 272 is not blown and switches the contacts so that the terminals T1 and T2 are connected. Furthermore, when the signal level of the connection line blown_fuse connected to the input side is at a high level, the changeover switch 291c determines that the fuse 272 is blown and switches the contacts so that the terminal T1 and the vertex T3 are connected.

[0150] The changeover switch 292c is an electronic component that switches contacts so that signals transmitted and received by the main SoC 101c via the connector 222c are transmitted and received at port D- of the sub SoC 201c, or are transmitted and received on the communication line D-_thr, bypassing the sub SoC 201c. As shown in FIG. 9, the changeover switch 292c has terminals T1 to T3. Terminal T1 is connected to the connector 222c, terminal T2 is connected to port D- of the sub SoC 201c, and terminal T3 is connected to the communication line D-_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 292c determines that the fuse 272 is not blown and switches its contacts so that terminal T1 and terminal T2 are connected. Furthermore, when the signal level of the connection line blown_fuse connected to the input side is at a high level, the changeover switch 292c determines that the fuse 272 is blown and switches the contacts so that the terminal T1 and the vertex T3 are connected.

[0151] The changeover switch 293c is an electronic component that switches contacts to transmit signals transmitted and received by the sub-SoC 201c via the connector 251c to the sub-SoC 301c, or to transmit and receive signals that have bypassed the sub-SoC 201c and passed through the communication line D+_thr to the sub-SoC 301c via the connector 251c. As shown in FIG. 9, the changeover switch 293c has terminals T1 to T3. The terminal T1 is connected to the connector 251c, the terminal T2 is connected to the port D2+ of the sub-SoC 201c, and the terminal T3 is connected to the communication line D+_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 293c determines that the fuse 272 is not blown and switches the contacts so that the terminals T1 and T2 are connected. Furthermore, when the signal level of the connection line blown_fuse connected to the input side is at a high level, the changeover switch 293c determines that the fuse 272 is blown and switches the contacts so that the terminal T1 and the vertex T3 are connected.

[0152] The changeover switch 294c is an electronic component that switches contacts to transmit signals transmitted by the sub-SoC 201c via the connector 252c to the sub-SoC 301c, or to transmit signals that have bypassed the sub-SoC 201c and passed through the communication line D-_thr to the sub-SoC 301c via the connector 252c. As shown in FIG. 9, the changeover switch 294c has terminals T1 to T3. The terminal T1 is connected to the connector 252c, the terminal T2 is connected to the port D2- of the sub-SoC 201c, and the terminal T3 is connected to the communication line D-_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 294c determines that the fuse 272 is not blown and switches its contacts so that the terminals T1 and T2 are connected. Furthermore, when the signal level of the connection line blown_fuse connected to the input side is at a high level, the changeover switch 294c determines that the fuse 272 is blown and switches the contacts so that the terminal T1 and the vertex T3 are connected.

[0153] Because USB serial communication using differential signals is a bidirectional signal, a problem occurs in that it can cause a malfunction of the sub-SoC 201c if a voltage is applied to the sub-SoC 201c that is not powered by the power supply 271. For this reason, the communication path on the peripheral device control board 30c side of the peripheral device control board 20c is also provided with the changeover switches 293c and 294c, as described above.

[0154] 9, the peripheral device control board 30c includes a sub-SoC 301c, a connector 321c, a connector 322c, a connector 331, a connector 332, and a fuse 372. The connector 331, the connector 332, the fuse 372, the power supply 370, and the power supply 371 are the same as those in the above-described embodiment.

[0155] The sub-SoC 301c is a computing device that controls the entire peripheral control board 30c. The sub-SoC 301c operates by receiving power from a power supply 371. Among the ports that the sub-SoC 301c has, port D+ and port D- are assigned for transmitting and receiving differential signals to perform serial communication with the peripheral control board 20c. In other words, the sub-SoC 301c and the sub-SoC 201c of the peripheral control board 20c perform data communication via USB serial communication using differential signals.

[0156] The connector 321c is a transmission / reception connector for inputting / outputting signals transmitted and received at port D+ of the sub-SoC 301c from / to the peripheral device control board 20c in serial communication between the sub-SoC 201c and the sub-SoC 301c. The connector 321c is connected to the connector 251c of the peripheral device control board 20c by a communication line.

[0157] The connector 322c is a transmission / reception connector for inputting / outputting signals transmitted and received at port D- of the sub-SoC 301c from / to the peripheral device control board 30c in serial communication between the sub-SoC 201c and the sub-SoC 301c. The connector 322c is connected to the connector 252c of the peripheral device control board 20c by a communication line.

[0158] As described above, the electronic device 1c according to this modification is configured to communicate with each other by serial communication using differential signals, such as USB. Even in this case, even if the power supply to the peripheral control board 20c connected in a daisy chain from the main body control board 10c is interrupted, the main body control board 10c can still communicate with the subsequent peripheral control board 30c connected in a daisy chain.

[0159] The main SoC 101c, the sub SoC 201c, and the sub SoC 301c correspond to the "first control device," the "second control device," and the "third control device," respectively, of the present invention.

[0160] (Variation 4) The electronic device according to this modification will be described, focusing on the differences from the electronic device 1 according to the above-described embodiment. In this modification, a configuration will be described in which a differential signal is used as a communication method, for example, serial communication by PCI (Peripheral Component Interconnect) Express.

[0161] Fig. 10 is a diagram showing an example of the circuit configuration of a main body control board and a peripheral device control board of an electronic device according to Modification 4. With reference to Fig. 10, the circuit configuration of a main body control board 10d and peripheral device control boards 20d and 30d of an electronic device 1d according to this modification will be described.

[0162] In the electronic device 1d shown in Figure 10, a main body control board 10d is connected in series to a peripheral device control board 20d and a peripheral device control board 30d in a daisy chain connection, and data is communicated between them via PCI Express serial communication using differential signals as the communication method. In this PCI Express serial communication, data is communicated using two signal lines (Tx+, Tx-) for transmitting differential signals and two signal lines (Rx+, Rx-) for receiving differential signals. The main body control board 10d, the peripheral device control board 20d, and the peripheral device control board 30d correspond to the "first board," "second board," and "third board" of the present invention, respectively.

[0163] 10, the main body control board 10d includes a main SoC 101d, connectors 121d to 124d, a connector 131, and a connector 132. The connectors 131, 132, and power supply 140 are the same as those in the above-described embodiment.

[0164] The main SoC 101d is a computing device that controls the entire main body control board 10d. The main SoC 101d operates by receiving power from a power supply 140. Among the ports possessed by the main SoC 101d, ports Tx+ and Tx- for transmitting differential signals and ports Rx+ and Rx- for receiving differential signals are assigned to perform serial communication with the peripheral device control board 20d. In other words, the main SoC 101d of the main body control board 10d and a sub-SoC 201d (described later) perform data communication via PCI Express serial communication using differential signals.

[0165] The connectors 121d and 122d are transmitting connectors for outputting differential signals transmitted from ports Tx+ and Tx- of the main SoC 101d, respectively, from the main body control board 10d in serial communication between the main SoC 101d and the sub SoC 201d. The connectors 121d and 122d are connected by communication lines to connectors 221d and 222d, respectively, of the peripheral device control board 20d, which will be described later.

[0166] The connectors 123d and 124d are receiving connectors for inputting differential signals received at ports Rx+ and Rx- of the main SoC 101d from the main control board 10d during serial communication between the main SoC 101d and the sub-SoC 201d. The connectors 123d and 124d are connected by communication lines to connectors 223d and 223d, respectively, of the peripheral device control board 20d, which will be described later.

[0167] 10, the peripheral device control board 20d includes a sub-SoC 201d, connectors 221d to 224d, a connector 231, a connector 232, connectors 251d to 254d, a fuse 272, a connector 261, a connector 262, a detection circuit 290, and changeover switches 291d to 298d. Note that the connectors 231, 232, the fuse 272, the connectors 261, 262, the detection circuit 290, the power supplies 270, and the power supplies 271 are the same as those in the above-described embodiment. The changeover switches 291d to 298d correspond to the "switching means" of the present invention.

[0168] The sub-SoC 201d is a computing device that controls the entire peripheral device control board 20d. The sub-SoC 201d operates by receiving power from the power supply 271. Among the ports of the sub-SoC 201d, ports Tx+ and Tx- for transmitting differential signals and ports Rx+ and Rx- for receiving differential signals are assigned for serial communication with the main body control board 10d. That is, the main SoC 101d of the main body control board 10d and the sub-SoC 201d perform data communication via PCI Express serial communication using differential signals. Furthermore, among the ports of the sub-SoC 201d, ports Tx2+ and Tx2- for transmitting differential signals and ports Rx2+ and Rx2- for receiving differential signals are assigned for serial communication with the peripheral device control board 30d. That is, the sub-SoC 201d of the peripheral device control board 20d and a sub-SoC 301d (described later) of the peripheral device control board 30d perform data communication by PCI Express serial communication using differential signals.

[0169] The connectors 221d and 222d are receiving connectors for inputting differential signals received at ports Rx+ and Rx- of the sub-SoC 201d from the main control board 10d during serial communication between the main SoC 101d and the sub-SoC 201d. The connectors 221d and 222d are also connected to terminals T1 of the changeover switches 291d and 292d, respectively. The connectors 221d and 222d are connected to connectors 121d and 122d of the main control board 10d by communication lines, respectively.

[0170] The connectors 223d and 224d are transmitting connectors for outputting differential signals transmitted from ports Tx+ and Tx- of the sub-SoC 201d from the main control board 10d during serial communication between the main SoC 101d and the sub-SoC 201d. The connectors 223d and 224d are connected to terminals T1 of the changeover switches 293d and 294d, respectively. The connectors 223d and 224d are connected to connectors 123d and 124d of the main control board 10d by communication lines, respectively.

[0171] The connectors 251d and 252d are transmitting connectors for outputting differential signals transmitted from ports Tx2+ and Tx2- of the sub-SoC 201d, respectively, from the peripheral device control board 20d in serial communication between the sub-SoC 201d and the sub-SoC 301d. The connectors 251d and 252d are also connected to terminals T1 of the changeover switches 295d and 296d, respectively. The connectors 251d and 252d are connected via communication lines to connectors 321d and 322d, described later, of the peripheral device control board 30d, respectively.

[0172] The connectors 253d and 254d are receiving connectors for inputting differential signals received at ports Rx2+ and Rx2- of the sub-SoC 201d from the peripheral device control board 20d during serial communication between the sub-SoC 201d and the sub-SoC 301d. The connectors 253d and 254d are also connected to terminals T1 of the changeover switches 297d and 298d, respectively. The connectors 253d and 254d are connected via communication lines to connectors 323d and 324d, described later, of the peripheral device control board 30d, respectively.

[0173] The changeover switches 291d and 292d are electronic components that switch contacts so that differential signals transmitted from the main SoC 101d via the connectors 221d and 222d are received by the ports Rx+ and Rx- of the sub SoC 201d, respectively, or are transmitted to the communication lines Tx+_thr and Tx-_thr, respectively, bypassing the sub SoC 201d. As shown in Fig. 10, the changeover switches 291d and 292d each have terminals T1 to T3. The terminal T1 is connected to the connectors 221d and 222d, respectively, the terminal T2 is connected to the ports Rx+ and Rx- of the sub SoC 201d, respectively, and the terminal T3 is connected to the communication lines Tx+_thr and Tx-_thr, respectively. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switches 291d and 292d determine that the fuse 272 is not blown and switch their contacts so that the terminals T1 and T2 are connected. When the signal level of the connection line blown_fuse connected to the input side is high, the changeover switches 291d and 292d determine that the fuse 272 is blown and switch their contacts so that the terminals T1 and T3 are connected.

[0174] The changeover switches 293d and 294d are electronic components that switch contacts so that differential signals received by the main SoC 101d and transmitted via the connectors 223d and 224d are transmitted from the ports Tx+ and Tx- of the sub SoC 201d, respectively, or are received by the communication lines Rx+_thr and Rx-_thr, respectively, bypassing the sub SoC 201d. As shown in Fig. 10, the changeover switches 293d and 294d each have terminals T1 to T3. The terminal T1 is connected to the connectors 223d and 224d, respectively, the terminal T2 is connected to the ports Tx+ and Tx- of the sub SoC 201d, respectively, and the terminal T3 is connected to the communication lines Rx+_thr and Rx-_thr, respectively. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switches 293d and 294d determine that the fuse 272 is not blown and switch their contacts so that the terminals T1 and T2 are connected. When the signal level of the connection line blown_fuse connected to the input side is high, the changeover switches 293d and 294d determine that the fuse 272 is blown and switch their contacts so that the terminals T1 and T3 are connected.

[0175] The changeover switches 295d and 296d are electronic components that switch contacts to transmit differential signals transmitted from the sub-SoC 201d via the connectors 251d and 252d to the sub-SoC 301d, respectively, or to transmit differential signals that have passed through the communication lines Tx+_thr and Tx-_thr, skipping the sub-SoC 201d, to the sub-SoC 301d via the connectors 251d and 252d, respectively. As shown in Fig. 10, the changeover switches 295d and 296d each have terminals T1 to T3. The terminal T1 is connected to the connectors 251d and 252d, respectively, the terminal T2 is connected to the ports Tx2+ and Tx2- of the sub-SoC 201d, respectively, and the terminal T3 is connected to the communication lines Tx+_thr and Tx-_thr, respectively. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switches 295d and 296d determine that the fuse 272 is not blown and switch their contacts so that the terminals T1 and T2 are connected. When the signal level of the connection line blown_fuse connected to the input side is high, the changeover switches 295d and 296d determine that the fuse 272 is blown and switch their contacts so that the terminals T1 and T3 are connected.

[0176] The changeover switches 297d and 298d are electronic components that switch contacts to receive from the sub-SoC 301d differential signals that have been received by the sub-SoC 201d and passed through the connectors 253d and 254d, respectively, or to receive from the sub-SoC 301d differential signals that have passed through the communication lines Rx+_thr and Rx-_thr, skipping the sub-SoC 201d, via the connectors 253d and 253d, respectively. As shown in Fig. 10, the changeover switches 297d and 298d each have terminals T1 to T3. The terminal T1 is connected to the connectors 253d and 254d, respectively, the terminal T2 is connected to the ports Rx2+ and Rx2- of the sub-SoC 201d, respectively, and the terminal T3 is connected to the communication lines Rx+_thr and Rx-_thr, respectively. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switches 297d and 298d determine that the fuse 272 is not blown and switch their contacts so that the terminals T1 and T2 are connected. When the signal level of the connection line blown_fuse connected to the input side is high, the changeover switches 297d and 298d determine that the fuse 272 is blown and switch their contacts so that the terminals T1 and T3 are connected.

[0177] In principle, there are no output elements that support partial power down for differential signals, which are high-speed signals. Therefore, if a voltage is applied to the sub-SoC 201d that is not powered on by the power supply 271, this may cause the sub-SoC 201d to malfunction. To address this problem, changeover switches 295d to 298d are also provided in the communication path of the peripheral device control board 20d on the peripheral device control board 30d side.

[0178] 10, the peripheral device control board 30d includes a sub-SoC 301d, connectors 321d to 324d, a connector 331, a connector 332, and a fuse 372. The connector 331, the connector 332, the fuse 372, the power supply 370, and the power supply 371 are the same as those in the above-described embodiment.

[0179] The sub-SoC 301d is a computing device that controls the entire peripheral control board 30d. The sub-SoC 301d operates by receiving power from a power supply 371. Among the ports that the sub-SoC 301d has, ports Tx+ and Tx- for transmitting differential signals and ports Rx+ and Rx- for receiving differential signals are assigned to perform serial communication with the peripheral control board 20c. In other words, the sub-SoC 301d and the sub-SoC 201d of the peripheral control board 20d perform data communication via PCI Express serial communication using differential signals.

[0180] The connectors 321d and 322d are receiving connectors for inputting differential signals received at the ports Rx+ and Rx- of the sub-SoC 301d from the peripheral device control board 20d during serial communication between the sub-SoC 201d and the sub-SoC 301d. The connectors 321d and 322d are connected to the connectors 251d and 252d of the peripheral device control board 20d by communication lines.

[0181] The connectors 323d and 324d are transmitting connectors for outputting differential signals transmitted from the ports Tx+ and Tx- of the sub-SoC 301d, respectively, from the peripheral device control board 20d in serial communication between the sub-SoC 201d and the sub-SoC 301d. The connectors 323d and 324d are connected to the connectors 253d and 254d of the peripheral device control board 20d by communication lines.

[0182] As described above, electronic device 1d according to this modification is configured to communicate with each other via serial communication using PCI Express with differential signals as the communication method. Even in this case, even if the power supply to peripheral control board 20d connected in a daisy chain from main body control board 10d is interrupted, main body control board 10d can still communicate with subsequent peripheral control board 30d connected in a daisy chain.

[0183] The main SoC 101d, the sub-SoC 201d, and the sub-SoC 301d correspond to the "first control device," the "second control device," and the "third control device," respectively, of the present invention.

[0184] (Variation 5) The electronic device according to this modification will be described, focusing on the differences from the electronic device 1 according to the above-described embodiment. In this modification, a configuration will be described in which parallel signals are used as a communication method, for example, parallel communication using IEEE1284, IDE, SCSI (Small Computer System Interface), PCI, etc.

[0185] Fig. 11 is a diagram showing an example of the circuit configuration of the main body control board and the peripheral device control board of an electronic device according to Modification 5. With reference to Fig. 11, the circuit configuration of the main body control board 10e and the peripheral device control boards 20e and 30e of the electronic device 1e according to this modification will be described.

[0186] In the electronic device 1e shown in Figure 11, a main body control board 10e is connected in series to a peripheral device control board 20e and a peripheral device control board 30e in a daisy chain connection, and data is communicated between them by parallel communication using parallel signals as the communication method. In this parallel communication, data is communicated using a multi-bit data bus signal (DATA) for transmitting and receiving data and multiple control signals (CMD_OUT, CMD_IN) for transmitting and receiving data. The main body control board 10e, the peripheral device control board 20e, and the peripheral device control board 30e correspond to the "first board," "second board," and "third board" of the present invention, respectively.

[0187] 11, the main body control board 10e includes a main SoC 101e, a plurality of connectors 121e, a plurality of connectors 122e, a plurality of connectors 123e, a connector 131, and a connector 132. The connectors 131, 132, and the power supply 140 are the same as those in the above-described embodiment.

[0188] The main SoC 101e is a computing device that controls the entire main body control board 10e. The main SoC 101e operates by receiving power from a power supply 140. Among the ports possessed by the main SoC 101e, multiple DATA ports for transmitting and receiving data bus signals and multiple CMD_OUT and CMD_IN ports for transmitting and receiving control signals are assigned for parallel communication with the peripheral device control board 20e. In other words, the main SoC 101e of the main body control board 10e and the sub-SoC 201e (described later) perform data communication through parallel communication using parallel signals.

[0189] The connector 121e is a transmission / reception connector for inputting / outputting data bus signals transmitted and received from the port DATA of the main SoC 101e to / from the main control board 10e in parallel communication between the main SoC 101e and the sub-SoC 201e. The connector 121e is connected to a connector 221e (described later) on the peripheral device control board 20e by a communication line.

[0190] The connector 122e is a transmission / reception connector for inputting / outputting control signals transmitted and received from the port CMD_OUT of the main SoC 101e to / from the main control board 10e in parallel communication between the main SoC 101e and the sub-SoC 201e. The connector 122e is connected to a connector 222e (described later) on the peripheral device control board 20e by a communication line.

[0191] The connector 123e is a receiving connector for inputting and outputting control signals transmitted and received from the port CMD_IN of the main SoC 101e to and from the main body control board 10e in parallel communication between the main SoC 101e and the sub SoC 201e. The connector 123e is connected to a connector 223e (described later) on the peripheral device control board 20e by a communication line.

[0192] 11, the peripheral device control board 20e includes a sub-SoC 201e, a plurality of connectors 221e, a plurality of connectors 222e, a plurality of connectors 223e, a connector 231, a connector 232, a plurality of IC circuits 245e, a plurality of IC circuits 246e, a plurality of connectors 224e, a plurality of connectors 225e, a plurality of connectors 226e, a fuse 272, a connector 261, a connector 262, a detection circuit 290, a plurality of changeover switches 291e, a plurality of changeover switches 292e, a changeover switch 293e, and a plurality of changeover switches 294e. Note that the connectors 231, 232, the fuse 272, the connectors 261, 262, the detection circuit 290, the power supply 270, and the power supply 271 are the same as those in the above-described embodiment. The changeover switches 291e to 294e correspond to the "switching means" of the present invention.

[0193] The sub-SoC 201e is a computing device that controls the entire peripheral control board 20e. The sub-SoC 201e operates by receiving power from a power supply 271. Among the ports of the sub-SoC 201e, multiple DATA ports for transmitting and receiving data bus signals and multiple CMD_OUT and CMD_IN ports for transmitting and receiving control signals are assigned for parallel communication with the main body control board 10e. That is, the main SoC 101e of the main body control board 10e and the sub-SoC 201e perform data communication through parallel communication using parallel signals. Furthermore, among the ports of the sub-SoC 201e, multiple DATA2 ports for transmitting and receiving data bus signals and multiple CMD_OUT2 and CMD_IN2 ports for transmitting and receiving control signals are assigned for parallel communication with the peripheral control board 30e. That is, the sub-SoC 201e of the peripheral device control board 20e and a sub-SoC 301e (described later) of the peripheral device control board 30e perform data communication by parallel communication using parallel signals.

[0194] The connector 221e is a transmission / reception connector for inputting and outputting data bus signals transmitted and received at the port DATA of the sub-SoC 201e from the main control board 10e during parallel communication between the main SoC 101e and the sub-SoC 201e. The connector 221e is also connected to the terminal T1 of the changeover switch 291e. The connector 221e is connected to the connector 121e of the main control board 10e by a communication line.

[0195] The connectors 222e are receiving connectors for inputting control signals received at the port CMD_IN of the sub-SoC 201e from the main control board 10e during parallel communication between the main SoC 101e and the sub-SoC 201e. The connectors 222e are also connected to the terminals T1 of the selector switches 292e. The connectors 221e are connected to the connectors 122e of the main control board 10e via communication lines.

[0196] The connectors 223e are transmission connectors for outputting control signals transmitted from the port CMD_OUT of the sub-SoC 201e to the main body control board 10e during parallel communication between the main SoC 101e and the sub-SoC 201e. The connectors 223e are also connected to the terminals T1 of the changeover switches 293e. The connectors 223e are connected to the connectors 123e of the main body control board 10e via communication lines.

[0197] The input side of the IC circuit 245e is connected to the port CMD_OUT2 of the sub-SoC 201e, and the output side is connected to the connector 225e, and the IC circuit 245e is an IC circuit for processing control signals inputted and outputted from the port CMD_OUT2 of the sub-SoC 201e.

[0198] The input side of the IC circuit 246e is connected to the port CMD_IN2 of the sub-SoC 201e, and the output side is connected to the connector 226e, and the IC circuit 246e is an IC circuit for processing control signals inputted and outputted from the port CMD_IN2 of the sub-SoC 201e.

[0199] The connector 224e is a transmission / reception connector for inputting and outputting data bus signals transmitted and received from the port DATA2 of the sub-SoC 201e to and from the peripheral device control board 20e during parallel communication between the sub-SoC 201e and the sub-SoC 301e. The connector 224e is also connected to the terminal T1 of the changeover switch 294e. The connector 224e is connected to a connector 321e (described later) of the peripheral device control board 30e via a communication line.

[0200] The connector 225e is a transmission connector for outputting control signals transmitted from the port CMD_OUT2 of the sub-SoC 201e from the peripheral device control board 20e in parallel communication between the sub-SoC 201e and the sub-SoC 301e. The connector 225e is connected to a connector 322e (described later) of the peripheral device control board 30e by a communication line.

[0201] The connector 226e is a receiving connector for inputting control signals received at the port CMD_IN2 of the sub-SoC 201e to the peripheral device control board 20e during parallel communication between the sub-SoC 201e and the sub-SoC 301e. The connector 226e is connected to a connector 323e (described later) of the peripheral device control board 30e by a communication line.

[0202] The changeover switch 291e is an electronic component that switches contacts to allow data bus signals transmitted and received from the main SoC 101e via the connector 221e to be transmitted and received at the port DATA of the sub SoC 201e, or to be transmitted and received at the communication line DATA_thr, bypassing the sub SoC 201e. As shown in FIG. 11 , the changeover switch 291e has terminals T1 to T3. The terminal T1 is connected to the connector 221e, the terminal T2 is connected to the port DATA of the sub SoC 201e, and the terminal T3 is connected to the communication line DATA_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 291e switches its contacts so that the terminal T1 and the terminal T2 are connected, assuming that the fuse 272 is not blown. Furthermore, when the signal level of the connection line blown_fuse connected to the input side is at a high level, the changeover switch 291e determines that the fuse 272 is blown and switches the contacts so that the terminal T1 and the vertex T3 are connected.

[0203] The changeover switch 292e is an electronic component that switches contacts so that a control signal transmitted from the main SoC 101e via the connector 222e is received by the port CMD_IN of the sub SoC 201e, or is transmitted to the communication line CMD_OUT_thr, bypassing the sub SoC 201e. As shown in FIG. 11 , the changeover switch 292e has terminals T1 to T3. The terminal T1 is connected to the connector 222e, the terminal T2 is connected to the port CMD_IN of the sub SoC 201e, and the terminal T3 is connected to the communication line CMD_OUT_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 292e determines that the fuse 272 is not blown and switches contacts so that the terminal T1 and the terminal T2 are connected. Furthermore, when the signal level of the connection line blown_fuse connected to the input side is at a high level, the changeover switch 292e determines that the fuse 272 is blown and switches the contacts so that the terminal T1 and the vertex T3 are connected.

[0204] The changeover switch 293e is an electronic component that switches contacts so that a control signal received by the main SoC 101e via the connector 223e is transmitted from the port CMD_OUT of the sub SoC 201e or is received by the communication line CMD_IN_thr, bypassing the sub SoC 201e. As shown in FIG. 11 , the changeover switch 293e has terminals T1 to T3. The terminal T1 is connected to the connector 223e, the terminal T2 is connected to the port CMD_OUT of the sub SoC 201e, and the terminal T3 is connected to the communication line CMD_IN_thr. When the signal level of the connection line blown_fuse connected to the input side is low, the changeover switch 293e determines that the fuse 272 is not blown and switches contacts so that the terminal T1 and the terminal T2 are connected. Furthermore, when the signal level of the connection line blown_fuse connected to the input side is at a high level, the changeover switch 293e determines that the fuse 272 is blown and switches the contacts so that the terminal T1 and the vertex T3 are connected.

[0205] The changeover switch 294e is an electronic component that switches contacts to transmit data bus signals transmitted from and received by the sub-SoC 201e via the connector 224e to and from the sub-SoC 301e, or to transmit data bus signals that have bypassed the sub-SoC 201e and passed through the communication line DATA_thr to and from the sub-SoC 301e via the connector 224e. As shown in FIG. 11 , the changeover switch 294e has terminals T1 to T3. The terminal T1 is connected to the connector 224e, the terminal T2 is connected to the port DATA2 of the sub-SoC 201e, and the terminal T3 is connected to the communication line DATA_thr. When the signal level of the connection line blown_fuse connected to the input side of the changeover switch 294e is low, the changeover switch 294e determines that the fuse 272 is not blown and switches its contacts so that the terminals T1 and T2 are connected. Furthermore, when the signal level of the connection line blown_fuse connected to the input side is high, the changeover switch 294e switches the contacts so that the terminal T1 and the vertex T3 are connected, assuming that the fuse 272 is blown. Because the data bus signal is a bidirectional signal, problems occur when voltage is applied to the sub-SoC 201e when the power supply 271 is not turned on. For this reason, the changeover switch 294e is also provided on the communication path of the peripheral device control board 30e side of the peripheral device control board 20e, as described above.

[0206] 11, the peripheral device control board 30e includes a sub-SoC 301e, a plurality of connectors 321e, a plurality of connectors 322e, a plurality of connectors 323e, a connector 331, a connector 332, and a fuse 372. Note that the connectors 331, 332, fuse 372, power supply 370, and power supply 371 are the same as those in the above-described embodiment.

[0207] The sub-SoC 301e is a computing device that controls the entire peripheral control board 30e. The sub-SoC 301e operates by receiving power from a power supply 371. Among the ports that the sub-SoC 301e has, a plurality of ports DATA for transmitting and receiving data bus signals and a plurality of ports CMD_OUT and CMD_IN for transmitting and receiving control signals are assigned to perform parallel communication with the peripheral control board 20e. In other words, the sub-SoC 301e and the sub-SoC 201e of the peripheral control board 20e perform data communication by parallel communication using parallel signals.

[0208] The connector 321e is a transmission / reception connector for inputting / outputting data bus signals transmitted and received at the port DATA of the sub-SoC 301e from / to the peripheral device control board 20e in parallel communication between the sub-SoC 201e and the sub-SoC 301e. The connector 321e is connected to the connector 224e of the peripheral device control board 20e by a communication line.

[0209] The connector 322e is a receiving connector for inputting control signals received at the port CMD_IN of the sub-SoC 301e from the peripheral device control board 20e during parallel communication between the sub-SoC 201e and the sub-SoC 301e. The connector 322e is connected to the connector 225e of the peripheral device control board 20e by a communication line.

[0210] The connector 323e is a transmission connector for outputting control signals transmitted from the port CMD_OUT of the sub-SoC 301e to the peripheral device control board 20e in parallel communication between the sub-SoC 201e and the sub-SoC 301e. The connector 323e is connected to the connector 226e of the peripheral device control board 20e by a communication line.

[0211] As described above, the electronic device 1e according to this modification is configured to communicate with each other by parallel communication using parallel signals as a communication method. Even in this case, even if the power supply to the peripheral control board 20e connected in a daisy chain from the main body control board 10e is cut off, the main body control board 10e can still communicate with the subsequent peripheral control board 30e connected in a daisy chain.

[0212] The main SoC 101e, the sub-SoC 201e, and the sub-SoC 301e correspond to the "first control device," the "second control device," and the "third control device," respectively, of the present invention.

[0213] (Variation 6) The electronic device according to this modification will be described, focusing on the differences from the electronic device 1 according to the above embodiment.

[0214] Fig. 12 is a diagram showing an example of the circuit configuration of the main body control board and peripheral device control board of an electronic device according to Modification 6. The circuit configuration of the peripheral device control boards 20f, 30f of the electronic device 1f according to this modification will be described with reference to Fig. 12. Note that the circuit configuration of the main body control board 10 of the electronic device 1f is similar to the circuit configuration of the main body control board 10 of the electronic device 1 according to the above-described embodiment.

[0215] The electronic device 1f shown in Fig. 12 includes a main body control board 10 for controlling the electronic device 1f main body, and peripheral control boards 20f and 30f for controlling other devices mounted on the electronic device 1f, such as optional devices. In the example of the electronic device 1f shown in Fig. 12, the peripheral control board 20 and the peripheral control board 30 are connected in series in this order via a daisy chain connection from the main body control board 10, and data is communicated between them using, for example, two-wire serial communication such as UART. The main body control board 10, the peripheral control board 20f, and the peripheral control board 30f correspond to the "first board," "second board," and "third board" of the present invention, respectively.

[0216] 12, the peripheral device control board 20f includes a sub-SoC 201, an IC circuit 211, a switching element 212, a connector 221, a connector 222, a connector 231, a connector 232, a switching element 241, an IC circuit 242, a connector 251, a connector 252, a load switch IC 273, a resistor R7, a connector 261, a connector 262, a resistor R2, a resistor R3, a changeover switch 291, and a changeover switch 292. Note that the configurations other than the configurations of the load switch IC 273 and the resistor R7 are the same as those of the above-described embodiment.

[0217] That is, the peripheral device control board 20f has a load switch IC 273 instead of the fuse 272 provided on the peripheral device control board 20 shown in Figure 1 above, and a fault signal output from the FAULT terminal of the load switch IC 273 is input to the changeover switch 291 and the changeover switch 292 instead of the detection circuit 290.

[0218] The load switch IC 273 is an IC circuit that stops the output of the 5V power supply 271 and outputs a fault signal (abnormal signal) from the FAULT terminal when it detects an overcurrent due to an abnormality such as a short circuit on the peripheral device control board 20f. In other words, the load switch IC 273 functions as a power supply cutoff device, similar to the fuse 272. The output specification of the FAULT terminal of the load switch IC 273 is, for example, an open-drain output format, and outputs a high level during normal operation via a pull-up resistor R7, and a low level during abnormal operation. Since the specifications of the load switch IC 273 may vary depending on the manufacturer, a similar circuit configuration can be achieved by adding a logic inversion circuit or an open-drain buffer. The FAULT signal output line of the load switch IC 273 is connected to the input side of the selector switches 291 and 292, as described above.

[0219] When the signal level of the fault signal input to the input side of the changeover switch 291 is low, the load switch IC 273 determines that an overcurrent has not been detected and switches the contacts so that terminals T1 and T2 are connected. When the signal level of the fault signal input to the input side of the changeover switch 291 is high, the load switch IC 273 determines that an overcurrent has been detected and switches the contacts so that terminals T1 and T3 are connected. In this case, the main SoC 101 of the main body control board 10 communicates data directly with the sub-SoC 301 of the peripheral device control board 30 via the communication lines Tx_thr and Rx_thr, without going through (skipping) the sub-SoC 201 of the peripheral device control board 20.

[0220] In this way, even if the power supply to the peripheral control board 20 connected in a daisy chain from the main control board 10 is cut off, communication can still be made with the subsequent peripheral control board 30 connected in a daisy chain from the main control board 10.

[0221] The load switch IC 273 corresponds to the "interrupter" and the "detector" of the present invention.

[0222] The aspects of the present invention are as follows. <1> a first substrate; a second substrate that receives power from the first substrate; a third substrate that receives power from the second substrate; a first control device mounted on the first substrate and controlling the operation of the first substrate; a second control device mounted on the second board, controlling the operation of the second board, and communicating with the first control device; a third control device mounted on the third board, controlling the operation of the third board, and communicating with the second control device; a cutoff means provided on the second substrate, for cutting off power supply from the first substrate when an overcurrent occurs on the second substrate; a detection means provided on the second substrate for detecting that the interruption has been caused by the interruption means; a switching means provided on the second substrate for switching between a communication path between the first control device and the second control device and a communication path between the first control device and the third control device; Equipped with The switching means is an electronic device that switches the communication path for communication between the first control device and the third control device when the detection means detects a cutoff by the cutoff means. <2> the second substrate is plural, a target substrate, which is the second substrate in a subsequent stage near the third substrate, receives power supply from the second substrate in a previous stage adjacent to the target substrate; the second control device of the target board communicates with the second control device of the second board adjacent to the target board in the previous stage; The switching means of the target board is switching between a communication path through which the second control device of the second board adjacent to the target board communicates with the second control device of the target board, and a communication path through which the second control device of the second board adjacent to the target board communicates with the control device of the subsequent board adjacent to the target board; When the detection means of the target board detects the interruption by the interruption means, the communication path is switched so that the second control device of the second board adjacent to the target board in the previous stage communicates with the control device of the next stage adjacent to the target board. <1> The electronic device is described in the above. <3> The first board, the second board, and the third board communicate with each other by two-wire serial communication of UART. <1> or <2> The electronic device is described in the above. <4> The first board, the second board, and the third board communicate with each other by three-wire serial communication. <1> or <2> The electronic device is described in the above. <5> The first board, the second board, and the third board communicate with each other using I2C two-wire serial communication. <1> or <2> The electronic device is described in the above. <6> The first board, the second board, and the third board communicate with each other using differential signals. <1> or <2> The electronic device is described in the above. <7> The first board, the second board, and the third board communicate with each other by parallel communication. <1> or <2> The electronic device is described in the above. <8> The first control device is a storage means for storing identification information of a device on a board to be a communication destination, the identification information being acquired at the time of startup; determining whether or not the identification information acquired at the time of startup and the identification information acquired at the previous startup and stored in the storage means are inconsistent; If there is a mismatch, it is detected that there is a possibility that the second substrate has been blocked by the blocking means. <1> or <2> The electronic device is described in the above. <9> the cutoff means and the detection means are a load switch IC that cuts off the power supply from the first board and outputs an abnormality signal when the overcurrent occurs, the switching means switches the communication path through which the first control device and the third control device communicate when the abnormality signal is output from the load switch IC. <1> ~ <8> 10. The electronic device according to claim 9, wherein the first and second electrodes are electrically connected to the first and second electrodes. <10> A communication method for an electronic device including a first substrate, a second substrate that receives power supply from the first substrate, and a third substrate that receives power supply from the second substrate, comprising: a first communication step in which a first control device mounted on the first board and controlling the operation of the first board communicates with a second control device mounted on the second board and controlling the operation of the second board; a second communication step in which the second control device communicates with a third control device mounted on the third board and controlling the operation of the third board; a cutting step in which a cutting means provided on the second board cuts off the power supply from the first board when an overcurrent occurs on the second board; a detecting step in which a detecting means provided on the second substrate detects that the second substrate has been interrupted by the interrupting means; a switching step in which a switching means provided on the second board switches between a communication path through which the first control device and the second control device communicate and a communication path through which the first control device and the third control device communicate; and In the switching step, when the detection means detects the interruption by the interruption means, the communication method switches to a communication path through which the first control device and the third control device communicate. [Explanation of symbols]

[0223] 1, 1a~1f Electronic equipment 10, 10a to 10e Main control board 20, 20_1, 20a~20f Peripheral control board 30, 30a~30f Peripheral control board 101, 101a~101e Main SoC 111 Switching element 112 IC circuit 140 Power supply 201, 201a~201e Sub-SoC 211 IC circuit 212 Switching element 231, 232 connectors 241 Switching element 241a, 241b IC circuit 242 IC circuit 242a IC circuit 243a IC circuit 245e, 246e IC circuit 270, 271 power supply 272 Fuse 273 Load Switch IC 290 Detection Circuit 290a transistor 291, 291a-291e, 292, 292a-292e, 293a-293e, 294c, 294d, 294e, 295d-298d Selector switch 301, 301a~301e Sub-SoC 311 IC circuit 312 Switching element 370, 371 power supply 372 Fuse 373 Load Switch IC [Prior art documents] [Patent documents]

[0224] [Patent Document 1] Japanese Patent Application Publication No. 2018-094720

Claims

1. a first substrate; a second substrate that receives power from the first substrate; a third substrate that receives power from the second substrate; a first control device mounted on the first substrate and controlling the operation of the first substrate; a second control device mounted on the second board, controlling the operation of the second board, and communicating with the first control device; a third control device mounted on the third board, controlling the operation of the third board, and communicating with the second control device; a cutoff means provided on the second substrate, for cutting off power supply from the first substrate when an overcurrent occurs on the second substrate; a detection means provided on the second substrate for detecting that the interruption has been caused by the interruption means; a switching means provided on the second substrate for switching between a communication path between the first control device and the second control device and a communication path between the first control device and the third control device; Equipped with The switching means is an electronic device that switches the communication path between the first control device and the third control device when the detection means detects the interruption by the interruption means.

2. the second substrate is a plurality of substrates, a target substrate, which is the second substrate in a subsequent stage near the third substrate, receives power supply from the second substrate in a previous stage adjacent to the target substrate; the second control device of the target board communicates with the second control device of the second board adjacent to the target board in the previous stage; The switching means of the target board is switching between a communication path for communication between the second control device of the second board in the preceding stage adjacent to the target board and the second control device of the target board, and a communication path for communication between the second control device of the second board in the preceding stage adjacent to the target board and the control device of the subsequent stage adjacent to the target board; The electronic device described in claim 1, wherein when the detection means of the target board detects a disconnection by the disconnection means, the communication path is switched so that the second control device of the second board in the previous stage adjacent to the target board and the control device in the subsequent stage adjacent to the target board communicate with each other.

3. 3. The electronic device according to claim 1, wherein the first board, the second board, and the third board communicate with each other using two-wire serial communication of UART.

4. The electronic device according to claim 1 , wherein the first board, the second board, and the third board communicate with each other using three-wire serial communication.

5. 3. The electronic device according to claim 1, wherein the first board, the second board, and the third board communicate with each other using I2C two-wire serial communication.

6. The electronic device according to claim 1 , wherein the first substrate, the second substrate, and the third substrate communicate with each other using differential signals.

7. The electronic device according to claim 1 , wherein the first board, the second board, and the third board communicate with each other using parallel communication.

8. The first control device a storage means for storing identification information of a device on a board to be a communication destination, the identification information being acquired at the time of startup; determining whether or not the identification information acquired at the time of startup and the identification information acquired at the previous startup and stored in the storage means are inconsistent; 3. The electronic device according to claim 1, wherein if there is a mismatch, it is detected that there is a possibility that the second board has been cut off by the cut-off means.

9. the cutoff means and the detection means are a load switch IC that cuts off the power supply from the first board and outputs an abnormality signal when the overcurrent occurs, 3. The electronic device according to claim 1, wherein the switching means switches the communication path between the first control device and the third control device when the abnormality signal is output from the load switch IC.

10. A communication method for an electronic device including a first substrate, a second substrate that receives power supply from the first substrate, and a third substrate that receives power supply from the second substrate, the method comprising: a first communication step in which a first control device mounted on the first board and controlling the operation of the first board communicates with a second control device mounted on the second board and controlling the operation of the second board; a second communication step in which the second control device communicates with a third control device mounted on the third board and controlling the operation of the third board; a cutting step in which a cutting means provided on the second board cuts off power supply from the first board when an overcurrent occurs on the second board; a detecting step in which a detecting means provided on the second substrate detects that the second substrate has been interrupted by the interrupting means; a switching step in which a switching means provided on the second board switches between a communication path through which the first control device and the second control device communicate and a communication path through which the first control device and the third control device communicate; and In the switching step, when the detection means detects a cutoff by the cutoff means, the communication path is switched to a path for communication between the first control device and the third control device.

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