Memory module and shape measuring machine

Abstract

To provide a memory module and a shape measuring machine for suppressing occurrences of defects of a volatile memory in a memory module capable of suppressing battery consumption.SOLUTION: A memory module 1 includes: an SRAM 132, which is a volatile memory; a power supply path L1 for supplying power of a battery 12 to the SRAM 132; a first capacitor 31 connected to the power supply path L1 in a parallel relationship with the SRAM 132; a discharge resistor 33 connected to the power supply path L1 in a parallel relationship with the first capacitor 31; a battery switch 41 for switching an on state of connecting the power supply path L1 to the battery and an off state of connecting the power supply path L1 to a discharge switch path L2; and a discharge switch 42 for connecting a discharge resistor 33 to ground while the battery switch 41 is switched from the on state to the off state and an optional electric charge flows from the power supply path L1 to the discharge switching path L2 via the battery switch 41.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a memory module having a volatile memory and a shape measuring instrument. [Background technology]

[0002] Conventionally, volatile memories such as SRAM and DRAM are used as memories for temporarily storing programs and data. This volatile memory has a fast response, but cannot retain data when it is not supplied with power. Therefore, there are electronic devices that maintain the data in the volatile memory by using battery power when the external power supply is cut off (for example, see Patent Document 1).

[0003] Conventionally, a shape measuring machine for measuring the surface roughness of a workpiece requires measurement conditions including various setting parameters in order to perform a measurement operation (see, for example, Patent Document 2). Such measurement conditions are written into the above-mentioned volatile memory, enabling a quick measurement operation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-266476 [Patent Document 2] Patent Publication No. 2022-89103 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, in an electronic device having a battery as disclosed in Patent Document 1, if the electronic device is not used for a long period of time, it is desirable to cut off the battery power in order to suppress battery consumption. The present inventors have studied cutting off the battery power to a volatile memory and found the following problems. First, assume a memory module having a volatile memory and a battery switch that turns on and off the connection between the battery and the volatile memory. In this memory module, when the battery switch is switched from on to off, the voltage of the volatile memory gradually drops due to the influence of a capacitor in the memory module. Here, if the battery switch is switched from off to on immediately after the voltage of the volatile memory falls below a voltage value capable of retaining data, the power may be turned on again in a state in which the data in the volatile memory is partially lost but not completely erased. In such a case, the processor may be restarted without being able to detect the partial data loss in the volatile memory, and may not be able to perform normal output. In particular, when the electronic device is a shape measuring device such as that described in Patent Document 2, the processor cannot read the measurement conditions that should be written in the volatile memory, resulting in a problem of an error.

[0006] The present invention aims to prevent the occurrence of defects in volatile memory in a memory module and a shape measuring instrument capable of reducing battery consumption. [Means for solving the problem]

[0007] A memory module according to one embodiment of the present invention includes a volatile memory, a power supply path that supplies battery power to the volatile memory, a first capacitor connected to the power supply path in a parallel relationship to the volatile memory, a discharge resistor connected to the power supply path in a parallel relationship to the first capacitor, a battery switch that switches between an on state that connects the power supply path to the battery and an off state that connects the power supply path to a discharge switching path, and a discharge switch that connects the discharge resistor to ground while the battery switch is switched from the on state to the off state and any charge flows from the power supply path to the discharge switching path via the battery switch. In such a configuration, when the battery switch is switched from an on state to an off state, the discharge resistor is connected to ground, and the first capacitor is discharged by the discharge resistor. As a result, the voltage applied to the volatile memory drops rapidly, and data in the volatile memory is quickly erased. Therefore, when the battery switch is continuously switched, after the battery power to the volatile memory is cut off, the data in the volatile memory can be completely erased before the power is re-applied. This makes it possible to prevent the power from being re-applied in a state in which the data in the volatile memory is partially lost, and to prevent the occurrence of a defect in which data is incompletely lost in the volatile memory.

[0008] It is preferable that the memory module according to one embodiment of the present invention further comprises a diode provided in the power supply path and preventing reverse current flow from the first capacitor to the battery, and a second capacitor connected to the power supply path in parallel with the first capacitor upstream of the diode. In this configuration, the discharge switch can be suitably turned on by utilizing the charge stored in the second capacitor.

[0009] In a memory module according to one aspect of the present invention, the discharge switch may be a semiconductor switch having a control terminal connected to the discharge switching path and connected between the discharge resistor and the ground.

[0010] In a memory module according to one aspect of the present invention, the discharge switch may include a light-emitting diode provided in the discharge switching path, and a phototransistor connected between the discharge resistor and the ground for receiving an optical signal from the light-emitting diode.

[0011] A shape measuring machine according to one embodiment of the present invention is a shape measuring machine for measuring the surface roughness of a workpiece, and includes a memory module described in any of the above, a battery that supplies power to the volatile memory, and a processor that performs measurement processing based on the measurement conditions stored in the volatile memory, and when the battery switch is switched from the off state to the on state, the processor writes default data of the measurement conditions to the volatile memory. In this configuration, the effect of the memory module described above prevents the occurrence of incomplete data loss in the volatile memory, so that the default data of the measurement conditions can be properly written to the volatile memory when the processor is restarted, and therefore the shape measuring instrument can perform normal measurement operations without generating errors due to the restart. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram illustrating a shape measuring instrument including a memory module according to the first embodiment, illustrating a state in which a battery switch is on (a normal use state of the shape measuring instrument). [Diagram 2] FIG. 2 is a diagram illustrating the shape measuring instrument including the memory module of the first embodiment, and is a diagram for explaining the off state of the battery switch (long-term storage state of the shape measuring instrument). [Diagram 3] FIG. 13 is a diagram illustrating a shape measuring machine including a memory module according to a second embodiment. [Figure 4] FIG. 13 is a diagram illustrating a shape measuring machine including a memory module according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [First embodiment] A first embodiment of the present invention will now be described with reference to the drawings. Fig. 1 shows a schematic diagram of a form measuring machine 10 including a memory module 1 according to this embodiment. This form measuring machine 10 is a device for measuring the roughness of a workpiece surface, and as shown in Fig. 1, includes the memory module 1, a power input terminal 11, a battery 12, a control unit 13, a power supply unit 14, and an operating unit 15. The form measuring machine 10 according to this embodiment is a small portable device that enables measurement at any location using power supplied from the battery 12.

[0014] The power supply input terminal 11 is, for example, a USB terminal, and is connected to an AC adapter 16 connected to a commercial power source. The AC adapter 16 converts the input AC of the commercial power source into DC, and supplies the converted DC as power supply power to the power supply input terminal 11. The power supply input terminal 11 is capable of outputting the power supply input from the AC adapter 16 to each supply destination.

[0015] The battery 12 is a secondary battery built into the shape measuring instrument 10. Similar to the power supply input terminal 11, the battery 12 is capable of outputting power from the power supply to each supply destination. The power input terminal 11 and the battery 12, together with a first diode 21 connected to the power input terminal 11 and a second diode 22 connected to the battery 12, form an OR circuit, and whichever has a higher voltage supplies the power source. For example, when the power input terminal 11 is connected to the AC adapter 16, the power source is supplied from the power input terminal 11, and the battery 12 is not consumed. When the power input terminal 11 is removed from the AC adapter 16, the power source is seamlessly supplied from the battery 12.

[0016] The control unit 13 includes a CPU (Central Processing Unit) 131, a volatile memory, a static random access memory (SRAM) 132, a non-volatile memory, a read only memory (ROM), etc. In addition, in FIG. 1, only the SRAM 132 is illustrated among various memories, and the other memories are not illustrated. CPU 131 is a processor of the present invention, which directly reads various processing programs such as a system program stored in ROM and performs measurement processing according to the read programs. SRAM 132 constitutes a cache memory, and CPU 131 stores necessary data in SRAM 132. CPU 131 can execute measurement processing at high speed based on the data stored in SRAM 132. Examples of measurement processing include processing for controlling operation unit 15 and arithmetic processing based on data acquired from operation unit 15.

[0017] In this embodiment, the data stored in the SRAM 132 includes measurement conditions including one or more setting parameters. The setting parameters include the type of roughness standard, the type of roughness parameter, the moving speed of the probe, the measurement range, the evaluation length, a filter to be applied to the data, and a calibration coefficient. Default data of the measurement conditions is pre-stored in the ROM. Moreover, SRAM 132 includes a data area for determining whether stored data has been lost. At startup, CPU 131 can detect data loss in SRAM 132 by determining whether or not there is a data area for determining whether stored data has been lost in SRAM 132. When CPU 131 detects data loss in SRAM 132, it stores initial data in SRAM 132, including default data of measurement conditions and a data area for determining whether stored data has been lost.

[0018] The power supply unit 14 is configured by, for example, a regulator, and supplies stable power to the CPU 131, the operating unit 15, etc. by receiving power from the power input terminal 11 or the battery 12. The power supply unit 14 is configured to include a switch that switches between on and off of power supply.

[0019] The operating unit 15 is a load that performs a measurement operation, which is an intended function of the profile measuring machine 10, by being controlled by the CPU 131. Specifically, the operating unit 15 includes a probe that detects the displacement of the workpiece surface, a mechanism for moving the probe, and an output unit that outputs the measurement results calculated by the CPU 131. Note that the configuration of the operating unit 15 can be substantially the same as that of a conventional device, and therefore a detailed description thereof will be omitted here.

[0020] The memory module 1 of this embodiment is configured to include the above-mentioned SRAM 132. This memory module 1 includes the above-mentioned SRAM 132, a power supply path L1 that supplies power from the battery 12 to the SRAM 132, a first capacitor 31, a second capacitor 32, and a discharge resistor 33 that are connected to the power supply path L1 in a parallel relationship, a battery switch 41 that turns on and off the connection to the battery 12, a discharge switch 42 that turns on and off the ground connection of the discharge resistor 33, and a discharge switching path L2 for turning on the discharge switch 42. Although not shown in the drawings, the memory module 1 includes a circuit board on which the above-mentioned elements are mounted. Elements other than the memory module 1 (such as the power input terminal 11, elements other than the SRAM 132 of the control unit 13, the power supply unit 14, etc.) may be mounted on this circuit board.

[0021] One end of the power supply path L1 is connected to the base point 411 of the battery switch 41, and the other end of the power supply path L1 is connected to the SRAM 132. In addition, the second diode 22 included in the above-mentioned OR circuit is provided on the power supply path L1. This second diode 22 corresponds to the diode of the present invention and prevents a reverse current flow to the battery 12. The power input terminal 11 and the power supply unit 14 are connected downstream of the second diode 22 in the power supply path L1.

[0022] The first capacitor 31 is connected to the power supply path L1 in parallel with the SRAM 132 on the downstream side of the second diode 22, and smoothes the voltage supplied to the SRAM 132. The second capacitor 32 is connected to the power supply path L1 upstream of the second diode 22 in parallel with the first capacitor 31.

[0023] The discharge resistor 33 is connected to the power supply path L1 in parallel with the first capacitor 31 on the downstream side of the second diode 22. The discharge resistor 33 is capable of discharging the charges of the first capacitor 31 and the second capacitor 32 when the battery switch 41 is switched to the off state and the discharge switch 42 is connected to ground.

[0024] The battery switch 41 is a one-circuit two-contact switch that selectively connects the power supply path L1 to the battery 12 or the discharge switching path L2. Specifically, the battery switch 41 has a base point 411 connected to the power supply path L1, a switching point 412 electrically connected to the battery 12, and a switching point 413 connected to one end of the discharge switching path L2. The battery switch 41 switches between an ON state (see FIG. 1) in which the power supply path L1 is electrically connected to the battery 12, and an OFF state (see FIG. 2) in which the power supply path L1 is electrically connected to the discharge switching path L2. The battery switch 41 is a manual switch, and the switching of the battery switch 41 is performed in response to a user operation on an operation unit (not shown), such as a button or a slide switch, provided on the shape measuring instrument 10. During the period when the form measuring instrument 10 can be normally used, the battery switch 41 is always maintained in the on state, regardless of the on / off state of the power supply unit 14. When the form measuring instrument 10 is to be stored for a long period of time, the power supply unit 14 is turned off, and then the battery switch 41 is switched from the on state to the off state. In other words, the battery switch 41 is a switch that switches the form measuring instrument 10 between a normal use state and a long-term storage state.

[0025] The discharge switch 42 is a semiconductor switch formed of, for example, an NchMOSFET, and is connected between the discharge resistor 33 and the ground. The discharge switch 42 has a gate terminal G serving as a control terminal connected to the discharge switching path L2, a drain terminal D connected in series to the discharge resistor 33, and a source terminal S connected to the ground. When a voltage is applied between the gate terminal G and the source terminal S, a current flows from the drain terminal D to the source terminal S. That is, the discharge switch 42 can switch between an open state in which the discharge resistor 33 is separated from the ground and a short-circuit state in which the discharge resistor 33 is connected to the ground, depending on the presence or absence of a voltage applied to the gate terminal G. In addition, although the discharge switch 42 is connected in series to the downstream side of the discharge resistor 33 in FIG. 1, it may be connected in series to the upstream side of the discharge resistor 33.

[0026] One end of the discharge switching path L2 is connected to the switching point 413 of the battery switch 41, and the other end of the discharge switching path L2 is connected to the gate terminal G of the discharge switch 42. In addition, the middle part of the discharge switching path L2 is connected to ground via a resistor 34. This resistor 34 is a pull-down resistor for reliably setting the potential of the gate terminal G of the discharge switch 42 to the ground potential when the battery switch 41 is in the on state (see FIG. 1).

[0027] Next, a description will be given of the operation of the memory module 1. In the following description, it is assumed that the power input terminal 11 is not connected to the AC adapter 16 (or the AC adapter 16 is not connected to a commercial power source) and the power supply from the power input terminal 11 is cut off.

[0028] 1, when the battery switch 41 is in an on state, power is supplied from the battery 12 to the SRAM 132. As a result, the SRAM 132 stores measurement conditions including various setting parameters. In addition, the first capacitor 31 and the second capacitor 32 are each charged with the power supplied from the battery 12, and remove noise components from the power. In this case, since the gate terminal G of the discharge switch 42 is kept at the ground potential, the discharge switch 42 is kept in an open state and no current flows through the discharge resistor 33. This makes it possible to suppress unnecessary power consumption by the discharge resistor 33.

[0029] When the user will not be using the shape measuring instrument 10 for a long period of time, for example, the user turns off the power supply unit 14 and then performs an operation to cut off the power of the battery 12. In response to this operation, the battery switch 41 is switched to the off state as shown in FIG.

[0030] When the battery switch 41 is switched from the on state to the off state, the charge of the circuit board on which each element of the memory module 1 is mounted is discharged. Among these, the charge discharged from the second capacitor 32 in particular flows into the discharge switching path L2 via the power supply path L1 and the battery switch 41, and a voltage is applied between the gate terminal G and the drain terminal D of the discharge switch 42 (see the arrow R1 in FIG. 2). As a result, the discharge switch 42 is short-circuited, and the first capacitor 31 is discharged by the discharge resistor 33 (see the arrow R2 in FIG. 2). When the discharge switch 42 is short-circuited, the second capacitor 32 is also discharged by the discharge resistor 33 (see the arrow R3 in FIG. 2). As a result, the charge remaining on the circuit board is rapidly discharged, and the voltage applied to the SRAM 132 is rapidly reduced, so that the data in the SRAM 132 is quickly erased.

[0031] Thereafter, when the user switches the battery switch 41 to the on state, the power of the battery 12 is again supplied to the SRAM 132 etc. Thereafter, when the power supply unit 14 is switched to the on state, the CPU 131 judges whether or not there is a data area for determining loss of stored data in the SRAM 132. If the CPU 131 judges that the data area does not exist in the SRAM 132, it detects data loss in the SRAM 132 and stores initial data including default data of the measurement conditions and the data area for determining loss of stored data in the SRAM 132. This allows the CPU 131 to reboot normally.

[0032] According to the memory module 1 of the present embodiment described above, when the battery switch 41 is continuously switched, after the power of the battery 12 to the SRAM 132 is cut off, the data in the SRAM 132 can be completely erased before the power is turned on again. This makes it possible to prevent the power from being turned on again in a state where the data in the SRAM 132 is partially lost, and to prevent the occurrence of a problem in which the data in the SRAM 132 is incompletely lost. As a result, the CPU 131 can correctly determine whether or not data is present in the SRAM 132, and can normally restart the system.

[0033] Furthermore, in the memory module 1 of this embodiment, when the battery switch 41 is turned off, the discharge switch 42 is automatically turned on by utilizing the discharge of electric charge within the memory module 1, and the discharge switch 42 is automatically turned off over time. Therefore, a controller for turning the discharge switch 42 on and off is not required. This allows the memory module 1 to be configured at low cost. Furthermore, since a power supply for the controller is not required, power consumption can be suitably suppressed.

[0034] In addition, the memory module 1 of this embodiment can prevent backflow of current to the battery 12 using the second diode 22, while utilizing the charge stored in the second capacitor 32 upstream of the second diode 22, thereby enabling the discharge switch 42 to be turned on appropriately.

[0035] In this embodiment, the discharge switch 42 is preferably a semiconductor switch such as a MOSFET that requires a sufficiently small gate-source voltage Vgs for turning on the discharge switch 42. This makes it possible to suitably ensure the on-period of the discharge switch 42. Moreover, it is preferable that the gate-source voltage Vgs required for turning on the discharge switch 42 is smaller than the data retaining voltage of the SRAM 132. This makes it possible to maintain the discharge switch 42 in a short-circuited state until the voltage of the first capacitor 31 decreases to the data retaining voltage of the SRAM 132 or lower, and therefore makes it possible to quickly erase the data in the SRAM 132.

[0036] The memory module 1 of this embodiment does not retain data in the SRAM 132 when the power is cut off, but erases the data quickly, so a large-capacity capacitor is not required. Therefore, the memory module 1 of this embodiment can be suitably used for a small shape measuring instrument 10.

[0037] In the form measuring machine 10 of this embodiment, as described above, the occurrence of an incomplete data loss state in the SRAM 132 is suppressed, so that when the CPU 131 is restarted, the default data of the measurement conditions can be normally written to the SRAM 132. Therefore, the form measuring machine 10 can perform a normal measurement operation without generating an error due to the restart.

[0038] [Second embodiment] A profile measuring machine 10A according to the second embodiment will be described with reference to Fig. 3. The profile measuring machine 10A according to the second embodiment has a configuration substantially similar to that of the profile measuring machine 10 according to the first embodiment. In the following, the same reference numerals are used for the same configuration as in the first embodiment, and the description thereof will be omitted or simplified.

[0039] In the shape measuring machine 10A of the second embodiment, the operating voltage of the operation unit 15 (not shown in FIG. 3) and the operating voltage of the control unit 13 are different from each other. Therefore, as shown in FIG. 3, the shape measuring machine 10A includes a first voltage conversion unit 51 that converts the power supply power supplied from the power supply input terminal 11 to a voltage for the control unit 13, a first power supply unit 14A that supplies the power supply power before the voltage conversion to the operation unit 15, a second voltage conversion unit 52 that converts the power supply power supplied from the battery 12 to a voltage for the control unit 13, a second power supply unit 14B that supplies the power supply power before the conversion to the operation unit 15, and a third power supply unit 14C that supplies the power supply power voltage-converted by the first voltage conversion unit 51 or the second voltage conversion unit 52 to the CPU 131, etc. Note that the first voltage conversion unit 51 is a voltage conversion circuit connected between the power supply input terminal 11 and the first diode 21, and the second voltage conversion unit 52 is a voltage conversion circuit connected between the battery 12 and the second diode 22.

[0040] In the memory module 1A according to the second embodiment, the SRAM 132 is supplied with power supply power that has been voltage converted by the second voltage conversion unit 52. In addition, a voltage dividing resistor 35 that adjusts the voltage applied to the gate terminal G of the discharge switch 42 is provided in the discharge switching path L2.

[0041] The memory module 1A according to the second embodiment described above can operate in the same manner as the memory module 1 according to the first embodiment. Specifically, when the battery switch 41 is switched from the on state to the off state while the power supply from the power supply input terminal 11 is cut off, a voltage is applied to the gate terminal G of the discharge switch 42 mainly due to the charge stored in the second capacitor 32 (see arrow R1 in FIG. 3). This causes the discharge switch 42 to be short-circuited, and the first capacitor 31 is discharged by the discharge resistor 33 (see arrow R2 in FIG. 3). When the discharge switch 42 is short-circuited, the second capacitor 32 is also discharged by the discharge resistor 33 (see arrow R3 in FIG. 3). As a result, the voltage applied to the SRAM 132 drops rapidly, and the data in the SRAM 132 is quickly erased. Therefore, similar to the profile measuring machine 10 of the first embodiment, the profile measuring machine 10A of the second embodiment can perform a normal measurement operation without generating an error due to restart.

[0042] [Third embodiment] A profile measuring machine 10B according to the third embodiment will be described with reference to Fig. 4. The profile measuring machine 10B according to the third embodiment has substantially the same configuration as the profile measuring machine 10 according to the first embodiment, except for the configuration of the discharge switch 42A. In the following, the same reference numerals are used for the same configuration as the first embodiment, and the description thereof will be omitted or simplified.

[0043] The discharge switch 42A of the third embodiment is configured by a photocoupler. Specifically, the discharge switch 42A includes a light-emitting diode 421 provided in the discharge switching path L2, and a phototransistor 422 connected between the discharge resistor 33 and the ground and receiving an optical signal from the light-emitting diode 421. When a current flows through the light-emitting diode 421, the light-emitting diode 421 emits light. While receiving light from the light-emitting diode 421, the phototransistor 422 is in a short-circuit state in which a current flows through the discharge resistor 33. That is, the phototransistor 422 can switch between an open state in which the discharge resistor 33 is separated from the ground and a short-circuit state in which the discharge resistor 33 is connected to the ground, depending on whether the light-emitting diode 421 emits light or not. In the third embodiment, one end of the discharge switching path L2 is connected to the switching point 413 of the battery switch 41, and the other end of the discharge switching path L2 is connected to ground.

[0044] The memory module 1B according to the third embodiment described above can operate in the same manner as the memory module 1 according to the first embodiment. Specifically, when the battery switch 41 is switched from the on state to the off state while the power supply from the power supply input terminal 11 is cut off, the charge stored in the second capacitor 32 mainly flows to the light emitting diode 421, causing the light emitting diode 421 to emit light (see arrow R1 in FIG. 4). This causes the phototransistor 422 to be short-circuited, and the first capacitor 31 is discharged by the discharge resistor 33 (see arrow R2 in FIG. 4). When the phototransistor 422 is short-circuited, the second capacitor 32 is also discharged by the discharge resistor 33 (see arrow R3 in FIG. 4). As a result, the voltage applied to the SRAM 132 drops rapidly, and the data in the SRAM 132 is quickly erased. Therefore, similar to the profile measuring machine 10 of the first embodiment, the profile measuring machine 10B of the third embodiment can perform a normal measurement operation without generating an error due to restart.

[0045] [Variations] The present invention is not limited to the above-described embodiments, and configurations obtained by modifications and improvements within the scope of the present invention that can achieve the object of the present invention are included in the present invention.

[0046] The form measuring machines 10, 10A, 10B of the above embodiments include diodes 21, 22 constituting an OR circuit to switch power between two power sources, the battery 12 and the AC adapter 16, and consume the power source with a higher voltage with priority. As a modification, the form measuring machines 10, 10A, 10B may include a priority power source switching function IC, instead of the OR circuit, that controls power source switching between the two power sources, the battery 12 and the AC adapter 16. This priority power source switching function IC may have a function of consuming the lower power source of the battery 12 and the AC adapter 16 with priority. Alternatively, the form measuring machines 10, 10A, 10B may include other means (circuits, semiconductors, etc.) for power source switching. Further, the shape measuring machines 10, 10A, 10B in the above embodiments are provided with two power supply paths through the battery 12 and the AC adapter 16, but it is sufficient that they are provided with at least a power supply path through the battery 12.

[0047] The memory modules 1, 1A, and 1B in the above embodiments include an SRAM 132 constituting a cache as the volatile memory of the present invention, but the present invention is not limited to this. For example, the SRAM 132 may be a buffer other than a cache. Furthermore, the volatile memory of the present invention may be a memory other than an SRAM, such as a DRAM.

[0048] Although the battery switch 41 in each of the above embodiments is a manual changeover switch, it may be an electronic changeover switch controlled by another control circuit or the like.

[0049] In the above-described embodiments, the discharge switch 42, 42A is an N-channel MOSFET or a photocoupler, but the present invention is not limited to this. For example, the discharge switch 42 in the first and second embodiments may be another semiconductor switch, such as a bipolar transistor or an IGBT (Insulated Gate Bipolar Transistor).

[0050] In the above embodiments, the discharge switch 42 is switched to the short-circuit state mainly by the charge stored in the second capacitor 32, but the present invention is not limited to this. For example, the discharge switch 42 may be switched to the short-circuit state by the stored charge in another capacitor connected to the power supply path L1.

[0051] In the above embodiments, the shape measuring instruments 10, 10A, and 10B are described, but the memory module of the present invention can be applied to any other electronic device. In any electronic device to which the memory module of the present invention is applied, the battery may be one that supplies power to at least the volatile memory. [Explanation of symbols]

[0052] 1, 1A, 1B... memory module, 10, 10A, 10B... shape measuring device, 11... power supply input terminal, 12... battery, 13... control unit, 131... CPU (processor), 132... SRAM (volatile memory), 14... power supply unit, 14A... first power supply unit, 14B... second power supply unit, 14C... third power supply unit, 15... operation unit, 16... AC adapter, 21... first diode, 22... second diode, 31... first capacitor capacitor, 32...second capacitor, 33...discharge resistor, 34...resistor, 35...resistor, 41...battery switch, 411...base point, 412...switching point, 413...switching point, 42, 42A...discharge switch, 421...light-emitting diode, 422...phototransistor, 51...first voltage conversion unit, 52...second voltage conversion unit, D...drain terminal, G...gate terminal, L1...power supply path, L2...discharge switching path, S...source terminal.

Claims

1. A volatile memory; a power supply path for supplying battery power to the volatile memory; a first capacitor connected to the power supply path in a parallel relationship with the volatile memory; a discharge resistor connected to the power supply path in parallel with the first capacitor; a battery switch that switches between an ON state in which the power supply path is connected to the battery and an OFF state in which the power supply path is connected to a discharge switching path; a discharge switch that connects the discharge resistor to ground while the battery switch is switched from the on state to the off state and any charge flows from the power supply path through the battery switch to the discharge switching path.

2. a diode provided in the power supply path and configured to prevent a reverse current flow from the first capacitor to the battery; 2. The memory module of claim 1, further comprising: a second capacitor connected to said power supply path in parallel relation to said first capacitor upstream of said diode.

3. 2. The memory module according to claim 1, wherein the discharge switch is a semiconductor switch having a control terminal connected to the discharge switching path and connected between the discharge resistor and the ground.

4. The discharge switch is A light emitting diode provided in the discharge switching path; 2. The memory module according to claim 1, further comprising: a phototransistor connected between said discharge resistor and said ground, said phototransistor receiving an optical signal from said light emitting diode.

5. A shape measuring machine for measuring the surface roughness of a workpiece, A memory module according to any one of claims 1 to 4, the battery providing power to the volatile memory; A processor that performs measurement processing based on the measurement conditions stored in the volatile memory, When the battery switch is switched from the off state to the on state, the processor writes default data of the measurement conditions to the volatile memory.

Images