Network Systems

Abstract

To appropriately set an identification number for each slave in a network system while suppressing voltage resistance. [Solution] A network system 1a includes a master M, slaves S1 to Sn, and wiring W connecting the master and the slaves. This wiring has a high-potential side wiring section H that starts from the master and connects the slaves in series, and a low-potential side wiring section L that folds back from the end of the high-potential side wiring section and connects the slaves and the master in the opposite order to the high-potential side wiring section. The master includes a constant current source that supplies a constant current I to the high-potential side wiring section. Each slave includes an internal slave resistor 2R provided in the high-potential side wiring section within that slave, an internal slave detection section AD that detects the potential difference between the high-potential side wiring section and the low-potential side wiring section within that slave, and an internal slave control section C that calculates the identification number of that slave from the potential difference detected by the internal slave detection section.

Description

[Technical Field]

[0001] The present invention relates to a network system including a master and one or more slaves. [Background technology]

[0002] Patent Documents 1 and 2 are cited as documents describing conventional network systems. The master described in Patent Document 1 includes a voltage supply means for supplying a voltage to an electric wire connecting multiple slaves in series, causing each slave to determine its identification information. Each slave includes a resistor connected in series with the resistors of the other slaves via an electric wire, a measurement means for measuring a divided voltage value as the voltage value across the resistor and a voltage value upstream of the resistor, and a determination means for determining its own identification information from the voltage value upstream of the resistor measured by the measurement means, the divided voltage value, and the voltage value supplied to the electric wire by the voltage supply means.

[0003] Patent Document 2 describes a communication network in which one master and multiple slaves are daisy-chained together via a pair of buses, one on the high potential side and one on the low potential side. Each slave includes a control circuit that controls communication with the master, a resistive element inserted into the high potential side bus downstream of the point where the control circuit is connected, and a potential difference detection means that detects the potential difference between the upstream terminal of the resistive element and the low potential side bus. The control circuit sets an ID for communication with the master according to the level of the potential difference detected by the potential difference detection means. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-192012 [Patent Document 2] Patent No. 4957813 Summary of the Invention [Problem to be solved by the invention]

[0005] In the prior art, as the number of slaves connected to a master increases, it may become more difficult to properly set the identification numbers of each slave, or the greater the number of slaves connected to a master, the higher the voltage resistance required.

[0006] In view of the above circumstances, the present invention has an object to appropriately set the identification number of each slave while suppressing the voltage resistance in a network system including a master and one or more slaves. [Means for solving the problem]

[0007] A network system according to the present invention includes a master, one or more slaves, and wiring connecting the master and the one or more slaves. The wiring includes a high-potential-side wiring section that starts from the master and connects the one or more slaves in series, and a low-potential-side wiring section that turns back from the end of the high-potential-side wiring section and connects the one or more slaves and the master in the opposite order to the high-potential-side wiring section. The master includes a constant current source that supplies a constant current to the high-potential-side wiring section or consumes a constant current from the low-potential-side wiring section. Each of the one or more slaves includes an internal slave resistor provided in at least one of the high-potential-side wiring section and the low-potential-side wiring section within the slave, an internal slave detection section that detects a potential difference between the high-potential-side wiring section and the low-potential-side wiring section within the slave, and an internal slave control section that calculates the slave's identification number from the potential difference detected by the internal slave detection section. [Effects of the Invention]

[0008] According to the present invention, in a network system including a master and one or more slaves, it is possible to appropriately set the identification number of each slave while suppressing the voltage resistance. [Brief explanation of the drawings]

[0009] [Figure 1A]FIG. 1 is an explanatory diagram showing a network system 1a according to a first embodiment. [Figure 1B] FIG. 1 is an explanatory diagram showing a network system 1b according to a first embodiment. [Figure 1C] FIG. 1 is an explanatory diagram showing a network system 1c according to a first embodiment. [Figure 1D] FIG. 1 is an explanatory diagram showing a network system 1d according to a first embodiment. [Figure 1E] 10 is a graph showing detected voltages in network systems 1a and 1b. [Figure 1F] 10 is a graph showing detected voltages in network systems 1c and 1d. [Figure 1G] FIG. 1 is an explanatory diagram showing a network system 1g according to a first embodiment. [Figure 1H] FIG. 1 is an explanatory diagram showing a network system 1h according to a first embodiment. [Figure 1I] FIG. 1 is an explanatory diagram showing a network system 1i according to a first embodiment. [Figure 1J] FIG. 1 is an explanatory diagram showing a network system 1α according to a first embodiment. [Figure 1K] FIG. 1 is an explanatory diagram showing a network system 1β according to a first embodiment. [Figure 2A] FIG. 10 is an explanatory diagram showing a network system 2a according to a second embodiment. [Figure 2B] FIG. 10 is an explanatory diagram showing a network system 2b according to a second embodiment. [Figure 2C] FIG. 10 is an explanatory diagram showing a network system 2c according to a second embodiment. [Figure 2D] FIG. 10 is an explanatory diagram showing a network system 2d according to a second embodiment. [Figure 2E] 10 is a graph showing detected voltages in network systems 2a to 2d. [Figure 2F] FIG. 10 is an explanatory diagram showing a network system 2α according to a second embodiment. [Figure 3A]FIG. 10 is an explanatory diagram showing a network system 3a according to a third embodiment. [Figure 3B] FIG. 10 is an explanatory diagram showing a network system 3b according to a third embodiment. [Figure 3C] 10 is a graph of detected voltages in the network system 3a. [Figure 3D] 10 is a graph of detected voltages in the network system 3b. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the embodiments described below.

[0011] First Embodiment 1A, the network system 1a includes a master M, n slaves S1, S2, ..., Sn (n is an integer equal to or greater than 1), and a termination circuit device T. The master M, slaves Sn, ..., S2, S1, and termination circuit device T are daisy-chain connected in this order by a serial communication bus CB.

[0012] The master M is a device that outputs commands to each slave and acquires information from each slave. The master M is, for example, a programmable logic controller (PLC) or a personal computer (PC), but is not limited to these and may be any upper control device that controls each slave.

[0013] A slave is a device that operates a driving mechanism based on an operation command from the master M, acquires information from input devices such as sensors, and outputs it to the master M. Slaves are, for example, drivers (amplifiers) for motors and actuators, and various sensors that detect position, angle, speed, temperature, voltage, current, luminosity, etc., but are not limited to these. They may be any driving mechanism or input device that is daisy-chained to the master M and whose operation is controlled by the master. Note that in the initial state, regardless of whether initial values ​​for the communication IDs (described in detail below) of the slaves S1 to Sn are set, each slave is assumed to be unable to communicate with the master M and other slaves. Then, by setting the communication ID of each slave as described below (even if an initial value has been set, it is overwritten), each slave becomes able to communicate with the master M and other slaves.

[0014] Furthermore, the master M, the slaves Sn, ..., S2, S1, and the termination circuit device T are connected by a wiring W having a high-potential side wiring portion H and a low-potential side wiring portion L, separate from the serial communication bus CB. The high-potential side wiring portion H connects the slaves Sn, ..., S2, and S1, and the termination circuit device T in series, in this order, starting from the master M. The low-potential side wiring portion L then connects the termination circuit device T, one or more slaves S1, S2, ..., Sn, and the master M in series, in this order, starting from the end of the high-potential side wiring portion H. In other words, the low-potential side wiring portion L connects the devices in the opposite order to the high-potential side wiring portion H. The termination circuit device T has a connection portion between the high-potential side wiring portion H and the low-potential side wiring portion L, in other words, a folded portion B of the wiring W. The end of the wiring W is connected to the reference potential terminal GND.

[0015] The master M is connected to the beginning of the wiring W and includes a constant current source that supplies a constant current I to the wiring W using a voltage V supplied from a voltage source as a power source, a detection circuit AD that detects the potential difference between the high-potential side wiring section H and the low-potential side wiring section L within the master M, a control circuit C that calculates the number n of slaves connected to the master M from the potential difference detected by the detection circuit AD, and a serial transceiver ST.

[0016] Each of the slaves S1 to Sn includes a detection circuit AD that detects the potential difference between the high-potential side wiring section H and the low-potential side wiring section L within the slave, and a resistor with a resistance of 2R (twice the resistance of R) inserted in the high-potential side wiring section H within the slave closer to the voltage source than the connection point with the detection circuit AD. Each of the slaves S1 to Sn further includes a control circuit C that calculates the communication ID (identification number) of the slave from the potential difference detected by the detection circuit AD within the slave, and a serial transceiver ST that performs serial communication with the master M and other slaves. The communication ID of a slave is an ID used to identify the slave when the master M and slaves S1 to Sn communicate via the serial communication bus CB.

[0017] The current consumption of the detection circuit AD in the master M is zero or negligibly small. The same applies to the detection circuits AD in the slaves S1 to Sn.

[0018] The resistance of the resistors included in each of the slaves S1 to Sn is all 2R. The resistor included in each slave may be a single resistor, or may be a group of multiple resistors combined in series or in parallel so that the combined resistance is 2R.

[0019] 1B shows a network system 1b. As shown in the figure, the resistor 2R provided in each of the slaves S1 to Sn may be inserted in the low-potential side wiring section L of the slave closer to the reference potential terminal GND than the connection point with the detection circuit AD. Also, the constant current source in the master M may be provided between the connection point with the detection circuit AD in the low-potential side wiring section L and the reference potential terminal GND, rather than in the high-potential side wiring section H. In this case, the constant current source consumes a constant current I from the low-potential side wiring section L.

[0020] 1C shows a network system 1c. As shown in the figure, the resistor 2R provided in each of the slaves S1 to Sn may be inserted in the high-potential side wiring section H within the slave closer to the return section B than the connection point with the detection circuit AD. Also, as in network system 1b, a constant current source may be provided in the low-potential side wiring section L within master M between the connection point with the detection circuit AD and the reference potential terminal GND.

[0021] 1D shows a network system 1d. As shown in the figure, the resistor 2R provided in each of the slaves S1 to Sn may be inserted in the low-potential side wiring part L within the slave closer to the return part B than the connection point with the detection circuit AD.

[0022] Next, the operation of this embodiment will be described. A constant current is supplied (in the case of network systems 1a and 1d) or consumed (in the case of network systems 1b and 1c) by a constant current source in master M. Each slave Sx (x is an integer between 1 and n) can appropriately set a communication ID using the voltage Vad_Sx detected by the detection circuit AD of that slave. When there are multiple slaves, a unique communication ID can be set for each slave. Furthermore, master M can detect a detection voltage Vad_M according to the number of connected slaves using the detection circuit AD of that master.

[0023] Table 1 shows the voltages detected by the detection circuits AD built into the master M and slave Sx in the network systems 1a and 1b (when n=3). When all devices are connected properly, it can be seen that the voltages detected by the detection circuits AD in each slave are different from each other. Using these voltages, each slave can determine a unique communication ID. [Table 1]

[0024] Table 1 also shows the detected voltage when a break or short circuit occurs in the wiring W between the slave S1 and the slave S2.

[0025] FIG. 1E is a graph of the voltages detected by the detection circuits AD built into the master M and slave Sx in the network systems 1a and 1b (where n=3). The vertical axis represents the detected value of the detection circuit AD, and the horizontal axis lists the master M and slaves S3 to S1. In other words, FIG. 1E is a graph of the detected voltages under normal conditions from Table 1 above. From this figure, it can be seen that the difference in potential detected by the detection circuits in any two adjacent slaves is 2IR.

[0026] Table 2 shows the voltages detected by the detection circuits AD built into the master M and slave Sx in network systems 1c and 1d (when n=3). As with network systems 1a and 1b shown in Table 1, when all devices are connected properly, it can be seen that the voltages detected by the detection circuits AD in each slave are different from each other. Using these voltages, the slave can determine a unique communication ID. [Table 2]

[0027] FIG. 1F is a graph of the voltages detected by the detection circuits AD built into the master M and slave Sx in the network systems 1c and 1d (where n=3). The vertical axis represents the detected value of the detection circuit AD, and the horizontal axis lists the master M and slaves S3 to S1. In other words, FIG. 1F is a graph of the detected voltages under normal conditions from Table 2 above. From this figure, it can be seen that the difference in potential detected by the detection circuits in any two adjacent slaves is 2IR.

[0028] In the network systems 1a to 1d, even when n is not 3, the voltage difference detected by the detection circuits in any two adjacent slaves is 2IR. Unlike conventional technology, where the voltage difference between two adjacent slaves decreases as the number of slaves increases, this allows for easy setting of a unique communication ID. Details will be described later.

[0029] In the network systems 1a to 1d, the control circuit C performs the calculations shown in Table 3 using the detected voltages Vad_M and Vad_Sx, the constant current I, and the resistance 2R (twice the resistance of the resistance R). Note that the function int(*) in the table is a function that returns the largest integer not exceeding the argument *. For example, int(5.8)=5. [Table 3]

[0030] The control circuit C of the master M calculates the number n of slaves using the formula shown in Table 3. The slave Sx calculates the communication ID using the formula shown in Table 3 and sets it as its own communication ID. In the network systems 1a to 1d, the communication ID of the slave Sx is set to x. The constant terms such as 0.5 and 1.5 present in the arguments of the function int are intended to suppress the influence of voltage detection errors. Of course, the constant terms are not limited to those shown in Table 3.

[0031] According to the network systems 1a to 1d of the first embodiment, the slave Sx can set a unique communication ID for itself, and the master M can calculate the number of slaves connected in the daisy chain, without performing serial communication between the master M and the slave Sx for setting and confirming the communication ID. Furthermore, when the communication ID of the slave Sx is set to x as shown in Table 3, the master M can recognize that the network system contains a slave S1 with a communication ID set to 1, a slave S2 with a communication ID set to 2, ..., and a slave Sn with a communication ID set to n. In this way, the master and all slaves are ready to perform serial communication.

[0032] According to the network systems 1a to 1d of the first embodiment, a single detection circuit that detects the potential difference between the high-potential side wiring section H and the low-potential side wiring section L is sufficient for each of the master and slaves. The common-mode input voltage and detection value of the detection circuit change in proportion to the combined resistance between the detection circuit and the reference potential terminal GND. This makes it possible to keep low the voltage of the voltage source located at the most upstream of the high-potential side wiring and the common-mode input range of the detection circuit that detects the potential difference between the high-potential side wiring and the low-potential side wiring. The master can also calculate the number of connected slaves.

[0033] On the other hand, in Patent Document 1, the power supply means located most upstream is a constant voltage source, and the detected voltage at the slave changes in inverse proportion to the number of connected slaves. Therefore, as the number of connected slaves increases, the difference in detected voltage between the slaves decreases, making it difficult to set a unique communication ID. Furthermore, in order to detect its own communication ID, each slave requires multiple detection circuits that detect the potential between the high-potential side wiring and the low-potential side wiring, and the voltage drop across a resistor inserted in the high-potential side wiring or the low-potential side wiring.

[0034] In Patent Document 2, the common-mode input voltage of the detection circuit changes in proportion to a quadratic function (n*(n-1) / 2) of the number n of slaves connected downstream. Therefore, the more slaves connected, the more a detection circuit AD with a wide common-mode input voltage range and a voltage source VB that supplies a high voltage are required.

[0035] According to the first embodiment, as shown in Figures 1E and 1F, the voltage Vad_Sx detected by the detection circuit of each slave and the voltage Vad_M detected by the detection circuit of master M are expressed as a linear function of n, so that it is possible to suppress the expansion of the common-mode input voltage range and also to suppress the voltage of the voltage source.

[0036] In this way, according to the first embodiment, it is possible to appropriately set the identification number of each slave while suppressing the voltage resistance.

[0037] The master M may be provided with a storage means (not shown) such as a nonvolatile memory that communicates with the master's control circuit C and stores the number of connected slaves. The slave Sx may be provided with a storage means (not shown) such as a nonvolatile memory that communicates with the slave's control circuit C and stores its own calculated communication ID. By comparing the communication ID and the number of slaves calculated each time with the values ​​stored in the storage means, it is possible to monitor whether the network system configuration has changed.

[0038] 1G as a network system 1g, each slave may include a switch SW for switching between connection and disconnection between the high-potential side wiring portion H and the low-potential side wiring portion L within the device. By turning off the switches SW for slaves Sn to S2 and turning on the switch SW only for slave S1, slave S1 can also function as a termination circuit device.

[0039] 1H, a slave TS1 dedicated to a termination arrangement may be provided, which includes a termination circuit device T. Also, a master MS may be provided which includes one or more slaves.

[0040] As shown in FIG. 1I, a network system 1i can be configured in which a master M, all slaves Sn to S1, and a terminating circuit device T are integrated.

[0041] As mentioned above, the resistor provided in each slave may be a single resistor, or may be a group of multiple resistors combined in series or parallel so that the combined resistance is 2R.

[0042] As shown in FIG. 1J as network system 1α, each slave may include a first resistor RS11 provided in the high-potential side wiring section H closer to the voltage source than the connection point with the detection circuit AD, and a second resistor RS12 provided in the low-potential side wiring section L closer to the reference potential terminal than the connection point with the detection circuit AD. The resistances of the first resistor RS11 and the second resistor RS12 may be determined arbitrarily as long as the combined resistance of both resistors is 2R. As an example, the resistance of the first resistor RS11 may be set to R, and the resistance of the second resistor RS12 may also be set to R. The operation of this network system 1α is similar to that of network systems 1a and 1b.

[0043] As shown in FIG. 1K as network system 1β, each slave may include a first resistor RS21 provided on the high-potential side wiring section H closer to the turn-back section B than the connection point with the detection circuit AD, and a second resistor RS22 provided on the low-potential side wiring section L closer to the turn-back section B than the connection point with the detection circuit AD. The resistances of the first resistor RS21 and the second resistor RS22 may be set arbitrarily as long as the combined resistance of the two resistors is 2R. As an example, the resistance of the first resistor RS21 may be set to 1.5R, and the resistance of the second resistor RS22 may be set to 0.5R. The operation of this network system 1β is similar to that of network systems 1c and 1d.

[0044] Second Embodiment 2A to 2D show network systems 2a to 2d, respectively. Explanation of the same configuration as the network system according to the first embodiment will be omitted, and only differences from the first embodiment will be explained. In the network systems 2a to 2d, each slave Sx has two resistors with resistance R instead of the resistor 2R of the first embodiment. This will be explained in detail below.

[0045] In the network system 2a shown in FIG. 2A, each slave is provided with a resistor R on the high-potential side wiring section H inside the slave, which is located closer to the voltage source and closer to the return section B than the connection point with the detection circuit AD. In the network system 2b shown in FIG. 2B, each slave has a resistor R arranged on the voltage source side of the connection point with the detection circuit AD in the high-potential side wiring section H inside the slave, and a resistor R arranged on the return section B side of the connection point with the detection circuit AD in the low-potential side wiring section L inside the slave. In the network system 2c shown in FIG. 2C, each slave includes a resistor R provided on the high-potential side wiring section H inside the slave closer to the return section B than the connection point with the detection circuit AD, and a resistor R provided on the low-potential side wiring section L inside the slave closer to the reference potential terminal GND than the connection point with the detection circuit AD. In the network system 2d shown in FIG. 2D, each slave is provided with a resistor R on the low-potential side wiring section L inside the slave, which is located closer to the reference potential terminal GND and closer to the return section B than the connection point with the detection circuit AD.

[0046] In each of the network systems 2a to 2d, the resistance of all of the 2n resistors in total is R. Each resistor may be a single resistor, or may be a group of multiple resistors combined in series or parallel so that the combined resistance is R.

[0047] Next, the operation of this embodiment will be described. A constant current I is supplied by a constant current source in the master M. Each slave Sx, which has two resistors, can appropriately set a communication ID required for serial communication through the serial communication bus CB using the voltage Vad_Sx detected by the detection circuit AD of that slave. If there are multiple slaves, a unique communication ID can be set for each slave. Furthermore, the master M can detect a detection voltage Vad_M according to the number of connected slaves using the detection circuit AD of that master.

[0048] Table 4 shows the voltages detected by the detection circuits AD built into the master M and slave Sx in the network systems 2a to 2d (when n=3). When all devices are connected normally, it can be seen that the voltages detected by each detection circuit AD are different from one another. [Table 4]

[0049] 2E is a graph of the voltages detected by the detection circuits AD built into the master M and slaves Sx in the network systems 2a to 2d (where n=3). The vertical and horizontal axes are the same as those in FIG. 1E according to the first embodiment, and therefore a description thereof will be omitted. As in the first embodiment, in this embodiment, the detected voltages of the master M and each slave Sx change at a constant rate relative to the number of slaves (2IR per slave).

[0050] In the network systems 2a to 2d, the control circuit C performs the calculations shown in Table 5 from the detected voltages Vad_M and Vad_Sx, the constant current I, and the resistance R. [Table 5]

[0051] The control circuit C of the master M calculates the number of slaves n using the formula shown in Table 5. The slave Sx calculates the communication ID using the formula shown in Table 5 and sets it as its own communication ID.

[0052] In the second embodiment, as described above, each slave Sx has a resistor either on the high potential side wiring section H closer to the master M than the connection point with the detection circuit AD or on the low potential side wiring section L closer to the master M than the connection point with the detection circuit AD. Furthermore, each slave Sx has a resistor either on the high potential side wiring section H closer to the termination circuit device T than the connection point with the detection circuit AD or on the low potential side wiring section L closer to the termination circuit device T than the connection point with the detection circuit AD.

[0053] Therefore, in the slave Sn (FIG. 2A) of the network system 2a, the first connector group C1, which is composed of the connector C1a of the high-potential side wiring section H connected to the master M and the connector C1b of the low-potential side wiring section L, can be connected to the terminal circuit device T. At the same time, in the slave Sn (FIG. 2A) of the network system 2a, the second connector group C2, which is composed of the connector C2a of the high-potential side wiring section H connected to the terminal circuit device T and the connector C2b of the low-potential side wiring section L, can be connected to the master M. In either case, the detection voltages Vad_M and Vad_Sx of the detection circuit AD do not change. In other words, either the first connector group C1 or the second connector group C2 can be the master M side, and the other can be the terminal circuit device T side. In the daisy-chain connection, it is no longer necessary to distinguish between the master M side and the terminal circuit device T side. The same applies to the other slaves in the network system 2a and all the slaves in the network systems 2b to 2d.

[0054] Additionally, in the second embodiment, as in the first embodiment, it is possible to appropriately set the identification number of each slave while suppressing the voltage resistance.

[0055] Each slave may include multiple resistors connected in series or parallel. As shown in FIG. 2F as a network system 2α, each slave may include a first resistor RS31 provided in the high-potential wiring section H closer to the voltage source than the connection point with the detection circuit AD, and a second resistor RS32 provided in the low-potential wiring section L closer to the reference potential terminal than the connection point with the detection circuit AD. Each slave may also include a third resistor RS33 provided in the high-potential wiring section H closer to the turn-back section B than the connection point with the detection circuit AD, and a fourth resistor RS34 provided in the low-potential wiring section L closer to the turn-back section B than the connection point with the detection circuit AD. The resistances of the first resistor RS31 and the second resistor RS32 may be determined arbitrarily as long as the combined resistance of the two resistors is R. The resistances of the third resistor RS33 and the fourth resistor RS34 may be determined arbitrarily as long as the combined resistance of the two resistors is R. The operation of this network system 2α is similar to that of the network systems 2a to 2d.

[0056] <Third embodiment> FIG. 3A shows a network system 3a. Explanation of the same configuration as the network systems according to the first and second embodiments will be omitted, and only differences from the two embodiments will be explained. In the network system 3a, the termination circuit device T has a resistor R' provided at the folded portion B of the wiring W. The resistance R' can be set arbitrarily, but for simplicity, hereinafter, R' = R.

[0057] An abnormal range is set for the detection voltage of each detection circuit AD. If a voltage in the abnormal range is detected, it means that an abnormality such as a break or short circuit has occurred.

[0058] Furthermore, as shown in FIG. 3B as a network system 3b, the master M has a resistor R″ provided in the high-potential side wiring section H within the master, closer to the termination circuit device T than the connection point with the detection circuit AD. The resistance R″ can also be set arbitrarily, but for simplicity, let R″=R.

[0059] Next, the operation of this embodiment will be described. In the master M, a constant current I generated from a voltage source V is supplied or consumed, and two resistors with resistance R are built into the slave Sx, and a resistor with resistance R' is provided at the return section B. This allows each slave Sx to appropriately set a communication ID using the voltage Vad_Sx detected by the detection circuit AD of that slave. When there are multiple slaves, a unique communication ID can be set for each slave. Furthermore, the master M can detect a detection voltage Vad_M according to the number of connected slaves using the detection circuit AD of that master.

[0060] Table 6 shows the detected voltages in network system 3a, and Table 7 shows the detected voltages in network system 3b. When all devices are connected normally, the voltages detected by the detection circuit AD built into slave Sx are all different, and it can be seen that the ID calculated from these voltages is also unique. [Table 6] [Table 7]

[0061] 3C and 3D are graphs of the detected voltages in the network systems 3a and 3b, respectively. The vertical and horizontal axes are the same as those in FIG. 1E according to the first embodiment, but abnormal regions are newly indicated by shading. As in the first embodiment, the detected voltages of the master M and each slave Sx change at a constant rate relative to the number of slaves (2IR per slave).

[0062] In the network systems 3a and 3b, the control circuit C performs the calculations shown in Table 8 from the detected voltages Vad_M and Vad_Sx, the constant current I, and the resistance R. [Table 8]

[0063] The control circuit C of the master M calculates the number n of slaves using the formula shown in Table 8. The slave Sx calculates the communication ID using the formula shown in Table 8 and sets it as its own communication ID.

[0064] Tables 9 and 10 are abnormality region determination tables for network systems 3a and 3b, respectively. Here, N is the maximum allowable number of slave connections. If the detection voltages Vad_M and Vad_Sx are within the abnormal region shown in Table 9 or Table 10, an abnormality such as a break or short circuit between the high-potential side wiring and the low-potential side wiring can be detected. [Table 9] [Table 10]

[0065] Unlike Table 9, in Table 10, many of the abnormal regions are the same for the master M and the slave Sx, so the control circuit C can standardize the determination of whether it is inside or outside the abnormal region.

[0066] The abnormal regions shown in Table 10 will be explained with reference to Table 11. [Table 11]

[0067] Master M determines whether the calculated number of connected slaves, n, satisfies formula (1) in Table 11. Here, N is the upper limit of the number of connected slaves and is a positive integer not exceeding (V / 2IR)-1. If formula (1) is not satisfied, master M determines that an abnormality has occurred in network system 3b.

[0068] When formula (1) is satisfied, the master M then determines whether the calculated number of slave units n satisfies formula (2) in Table 11 (whether the error from the normal value exceeds the threshold). Here, w is the normal region width and is any value satisfying 0 < w < 1. When w = 0.5, the normal region and the abnormal region have the same width. When formula (2) is satisfied, the master M determines that the number of slave connections n is normal; otherwise, the master M determines that an abnormality has occurred in the network system 3b.

[0069] The slave Sx determines whether the calculated communication ID, that is, x, satisfies formula (3) in Table 11. When formula (3) is not satisfied, the slave Sx determines that an abnormality has occurred in the network system 3b.

[0070] When formula (3) is satisfied, the slave Sx then determines whether the calculated communication ID satisfies formula (4) in Table 11 (whether the error from the normal value exceeds the threshold). When formula (4) is satisfied, the slave Sx determines that the calculated communication ID is normal; otherwise, the slave Sx determines that an abnormality has occurred in the network system 3b.

[0071] The boundary voltages of the abnormal regions in Tables 9 and 10 were set as the intermediate voltages between normal and abnormal in Tables 6 and 7. However, this is not limited to this, and the boundary voltage of the abnormal region may be set to be biased towards either the normal or abnormal state.

[0072] <000034 In addition, in the calculation of the communication ID of the slave Sx in Tables 9 and 10, the detection voltage at which the communication ID is calculated as N + 1 is regarded as an excessive slave connection and is set as an abnormal region.

[0073] In addition, in the third embodiment as well, similar to the first embodiment, each slave identification number can be appropriately set while suppressing the withstand voltage. <00

[0074] Furthermore, the network systems according to the second and third embodiments can also be implemented using the modifications (FIGS. 1G to 1I) mentioned in the first embodiment. Similarly, the network systems according to the second and third embodiments include a constant current source that supplies a constant current I to the high-potential side wiring section H, but can also be implemented using a constant current source that consumes a constant current I from the low-potential side wiring section L.

[0075] The following notes are provided regarding the embodiments described above. <Appendix 1> Master and one or more slaves; Wiring connecting the master and the one or more slaves; A network system comprising: The wiring is a high-potential side wiring section that connects the one or more slaves in series starting from the master; a low-potential side wiring section that is folded back from the end of the high-potential side wiring section and connects the one or more slaves and the master in the opposite order to that of the high-potential side wiring section; and the master includes a constant current source that supplies a constant current to the high-potential side wiring portion or consumes a constant current from the low-potential side wiring portion; Each of the one or more slaves a slave internal resistor provided in at least one of the high potential side wiring portion and the low potential side wiring portion in the slave; a detection unit in the slave that detects a potential difference between the high potential side wiring portion and the low potential side wiring portion in the slave; an intra-slave control unit that calculates an identification number of the slave from the potential difference detected by the intra-slave detection unit; Equipped with Network system. <Appendix 2> The master a detection unit in the master that detects a potential difference between the high-potential side wiring portion and the low-potential side wiring portion in the master; an internal master control unit that calculates the number of slaves based on the potential difference detected by the internal master detection unit; Equipped with 2. The network system of claim 1. <Appendix 3> The slave internal resistor is one or more resistors provided on at least one of the high potential side wiring section and the low potential side wiring section on the master side of a connection point between the wiring and the slave detection section so that a combined resistance has a predetermined value; one or more resistors provided in at least one of the high-potential side wiring section and the low-potential side wiring section, closer to the return portion of the wiring than the connection point between the wiring and the intra-slave detection section, so that a combined resistance becomes the predetermined value; Including, 3. The network system according to claim 1 or 2. <Appendix 4> Further, a resistor is provided at a folded portion of the wiring, the slave control unit detects an abnormality in the wiring based on the potential difference detected by the slave detection unit; the master control unit detects an abnormality in the wiring based on the potential difference detected by the master detection unit; 3. The network system of claim 2. <Appendix 5> The master further includes an internal storage unit that stores the number of slaves calculated by the internal control unit of the master, and the internal control unit of the master compares the number of slaves calculated each time with the number of slaves stored in the internal storage unit of the master, Each of the one or more slaves further comprises an internal slave memory unit that stores the identification number of the slave calculated by the internal slave control unit, and the internal slave control unit compares the identification number of the slave calculated each time with the identification number stored in the internal slave memory unit. 5. The network system according to claim 2 or 4.

[0076] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical concept of the present invention. [Explanation of symbols]

[0077] 1a~1d, 1g~1i network system 2a~2d Network System 3a, 3b Network System M Master S1~Sn Slave AD detection circuit C Control circuit W wiring H High potential side wiring section L Low potential side wiring section

Claims

1. Master and one or more slaves; Wiring connecting the master and the one or more slaves; A network system comprising: The wiring is a high-potential side wiring section that connects the one or more slaves in series starting from the master; a low-potential side wiring section that turns back from the end of the high-potential side wiring section and connects the one or more slaves and the master in the opposite order to that of the high-potential side wiring section; and the master includes a constant current source that supplies a constant current to the high-potential side wiring portion or consumes a constant current from the low-potential side wiring portion; Each of the one or more slaves a slave internal resistor provided in at least one of the high potential side wiring portion and the low potential side wiring portion in the slave; a detection unit in the slave that detects a potential difference between the high potential side wiring portion and the low potential side wiring portion in the slave; an intra-slave control unit that calculates an identification number of the slave from the potential difference detected by the intra-slave detection unit; Equipped with Network system.

2. The master a detection unit in the master that detects a potential difference between the high-potential side wiring portion and the low-potential side wiring portion in the master; an internal master control unit that calculates the number of slaves based on the potential difference detected by the internal master detection unit; Equipped with The network system according to claim 1 .

3. The slave internal resistor is one or more resistors provided on at least one of the high-potential side wiring section and the low-potential side wiring section on the master side of a connection point between the wiring and the slave detection section so that a combined resistance has a predetermined value; one or more resistors provided in at least one of the high-potential side wiring section and the low-potential side wiring section, closer to the return portion of the wiring than the connection point between the wiring and the intra-slave detection section, so that a combined resistance becomes the predetermined value; Including, 3. The network system according to claim 1 or 2.

4. Further, a resistor is provided at a folded portion of the wiring, the slave control unit detects an abnormality in the wiring based on the potential difference detected by the slave detection unit; the master control unit detects an abnormality in the wiring based on the potential difference detected by the master detection unit; The network system according to claim 2 .

5. The master further includes an internal storage unit that stores the number of slaves calculated by the internal control unit of the master, and the internal control unit of the master compares the number of slaves calculated each time with the number of slaves stored in the internal storage unit of the master, Each of the one or more slaves further includes an internal slave storage unit that stores the slave's identification number calculated by the internal slave control unit, and the internal slave control unit compares the slave's identification number calculated each time with the identification number stored in the internal slave storage unit.

5. The network system according to claim 2 or 4.

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