Slave device

Abstract

To accomplish a slave device capable of performing safety control with high response performance by simply causing a user to select the wiring of a device and an application even the user does not have high expert knowledge.SOLUTION: A slave device 20 includes a safety input circuit 25, a safety output circuit 26, a storage unit 23 that stores multiple safety control applications, a safety control application designating unit 24 that can designate any of the safety control applications stored in the storage unit, and a control unit 21. When the safety control application designating unit designates a safety control application stored in the storage unit, the control unit loads and executes the designated safety control application from the storage unit to operate the safety output circuit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a slave device. [Background technology]

[0002] In the field of factory automation (FA), a safety network system for realizing safety control is known (for example, see Patent Document 1). A safety input / output device is a slave device in a safety network system that executes signal input / output between safety-related devices. Because it is a slave device, even when safety control is performed using the safety input / output device, control is performed on the safety control device side, which is the master device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7292558 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the settings for safety control on the safety control device side are generally done using dedicated PC software, and various steps are required to build the system, requiring a high level of specialized knowledge.In addition, the safety input / output device controls its output after receiving control from the safety control device, so it cannot achieve high response performance.

[0005] One aspect of the present invention aims to realize a slave device that can perform safety control with high response performance simply by wiring the devices and selecting an application, without requiring advanced specialized knowledge. [Means for solving the problem]

[0006] In order to solve the above problem, a slave device according to one embodiment of the present invention is a slave device that is connected to a network for safety control and communicates with a master device, and includes: a communication unit for communicating via the network; a safety input circuit having a plurality of input ports that receive input signals from an input device; a safety output circuit having a plurality of output ports that output output signals to an output device; a memory unit that stores a plurality of safety control applications each including an algorithm that determines an output signal based on input information indicated by the input signal; a safety control application designation unit that can designate any one of the plurality of safety control applications stored in the memory unit; and a control unit, and when a safety control application stored in the memory unit is designated by the safety control application designation unit, the control unit loads the safety control application from the memory unit, executes it, and operates the safety output circuit.

[0007] According to the above configuration, safety control with high response performance can be achieved simply by wiring the devices and selecting the application, without requiring a high level of specialized knowledge.

[0008] In the slave device, when the control unit receives an instruction from the master device via the communication unit to designate one of the safety control applications stored in the memory unit, the control unit may determine whether the safety control application designated by the master device matches the safety control application designated by the safety control application designation unit, and if they do not match, control the safety output circuit to stop output of the output signal.

[0009] According to the above configuration, safety control operations using multiple safety control applications stored in the memory unit of the slave device are performed under the supervision of the master device, thereby further improving safety.

[0010] In the slave device, when the safety control application designation unit does not designate any of the safety control applications stored in the memory unit, the control unit may transmit the input information to the master device via the communication unit and operate the safety output circuit in accordance with instructions from the master device.

[0011] According to the above configuration, the device can also be used as a general slave device that performs safety control operations in accordance with instructions from the master device.

[0012] In the slave device, when the slave device is started up, if the safety control application designation unit does not designate any of the safety control applications stored in the memory unit, the slave device may load and execute the safety control application received from the master device via the communication unit, and operate the safety output circuit.

[0013] According to the above configuration, a safety control application can be provided from outside the slave device, and safety control can be executed using the functions of the control unit included in the slave device.

[0014] In the slave device, the storage unit may be configured to include a removable storage medium that stores a plurality of the safety control applications.

[0015] In the slave device, the safety control application designation unit may be configured by a mechanical switch.

[0016] In the slave device, the safety control application designation unit may be configured to designate an operation mode of the slave device.

[0017] In the slave device, each unit of the slave device may be arranged across a plurality of connectable housings. [Effects of the Invention]

[0018] According to one aspect of the present invention, it is possible to realize a slave device that can perform safety control with high response performance simply by wiring the devices and selecting the application, without requiring advanced specialized knowledge. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram illustrating a network to which a slave device according to an embodiment of the present invention is applied. [Figure 2] FIG. 2 is a block diagram showing the configuration of a slave device according to an embodiment of the present invention. [Figure 3] FIG. 2 is a diagram illustrating a hardware configuration of a control unit in a slave device according to an embodiment of the present invention. [Figure 4] 10 is a flowchart illustrating an example of a processing procedure when the power supply of the slave device is turned on according to the present embodiment. [Figure 5] 10 is a flowchart showing an example of a processing procedure for a safety control operation of a slave device according to the present embodiment. [Figure 6] 10 is a flowchart illustrating an example of a processing procedure for monitoring a safety control application in a slave device according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] [Embodiment 1] Hereinafter, an embodiment according to one aspect of the present invention (hereinafter also referred to as "the present embodiment") will be described with reference to the drawings.

[0021] §1 Application Examples An example of a situation in which the present invention is applied will be described with reference to Figures 1 and 2. Figure 1 is a diagram showing a network to which a slave device according to an embodiment of the present invention is applied. Figure 2 is a block diagram showing the configuration of a slave device according to an embodiment of the present invention.

[0022] As shown in FIGS. 1 and 2, a slave device 20 according to an embodiment of the present invention in this application example includes a communication unit 22, is connected to a network 1, and communicates with a master device .

[0023] The slave device 20 includes a communication unit 22, a safety input circuit 25, and a safety output circuit 26. The safety input circuit 25 has a plurality of input ports P1 to P4 and receives input signals from an input device 50. The safety output circuit 26 has a plurality of output ports P5 to P8 and outputs output signals to an output device 60.

[0024] The slave device 20 further includes a storage unit 23, a control unit 21, and a safety control application designation unit 24. The storage unit 23 stores a plurality of safety control applications, each including an algorithm for determining the output signal based on input information indicated by the input signal. The safety control application designation unit 24 enables designation of any one of the plurality of safety control applications stored in the storage unit 23.

[0025] When a safety control application stored in the memory unit 23 is specified by the safety control application specification unit 24, the control unit 21 loads the safety control application from the memory unit 23, executes it, and operates the safety output circuit 26.

[0026] Therefore, the slave device 20 can independently perform safety control of the output device 60 without being controlled by the master device 10. Since safety control is performed by the slave device 20 without the intervention of the master device 10, safety control can be performed with high response performance. Furthermore, safety control can be achieved without requiring advanced specialized knowledge, simply by connecting the input device 50 to the multiple input ports P1 to P4, connecting the output device 60 to the multiple output ports P5 to P8, and selecting (specifying) a safety control application by the safety control application specification unit 24.

[0027] §2 Configuration example <Network> The slave device 20 according to the embodiment of the present invention will be described in more detail with reference to FIGS.

[0028] 1, network 1 is an industrial network also called a field network used in the field of factory automation (FA). Network 1 includes a master device 10 and multiple slave devices 20. A safety controller can be applied to the master device 10.

[0029] The input devices 50 connected to the input ports P1 to P4 of the slave device 20 are, for example, sensors such as light curtains, cameras, etc. The output devices 60 connected to the output ports P5 to P8 of the slave device 20 are, for example, controllers and actuators for robots, machine tools, etc.

[0030] <Slave device> As shown in FIG. 2, the slave device 20 includes a communication unit 22, a safety input circuit 25, a safety output circuit 26, a storage unit 23, a control unit 21, and a safety control application designation unit 24.

[0031] The communication unit 22 performs communication via the network 1. The safety input circuit 25 has a plurality of input ports P1 to P4 that receive input signals from the input device 50. The safety output circuit 26 has a plurality of output ports P5 to P8 that output output signals to the output device 60.

[0032] The storage unit 23 stores a plurality of safety control applications including an algorithm for determining the output signal based on input information indicated by the input signals received by the input ports P1 to P4. The storage unit 23 is configured with a non-volatile memory. The storage unit 23 may be configured to include a removable storage medium such as an SD card.

[0033] The safety control application designation unit 24 makes it possible to designate any one of a plurality of safety control applications stored in the storage unit 23. The safety control application designation unit 24 is, for example, a mechanical switch such as a rotary switch.

[0034] The safety control application designation unit 24 allows a safety control application to be alternatively designated. The safety control application designation unit 24 has a plurality of numbers, and by switching the numbers, a safety control application can be alternatively designated. The safety control application designation unit 24 transmits the designated number to the control unit 21.

[0035] As an example, in the slave device 20, the safety control application designation unit 24 can designate numbers from 0 to 15. A plurality of safety control applications stored in the storage unit 23 are assigned to the numbers "1" to "14." A plurality of safety control applications are stored one by one in the areas in the storage unit 23 corresponding to the numbers "1" to "14." The number in the safety control application designation unit 24 and one of the plurality of safety control applications stored in the storage unit 23 uniquely correspond to each other.

[0036] The number "0" is assigned to a safety control application in which the master device 10 performs the function of the safety processing part 216. The number "15" is assigned to a safety control application that receives and operates the safety control application from the master device 10. No safety control application is stored in the areas of the storage unit 23 corresponding to the numbers "0" and "15".

[0037] When the safety control application designation unit 24 designates a safety control application stored in the storage unit 23, the control unit 21 loads the safety control application from the storage unit 23, executes it, and operates the safety output circuit 26. The control unit 21 loads the designated safety control application from the storage unit 23, executes it, and operates the safety output circuit 26 in accordance with the result determined based on the input signal obtained by the safety control application.

[0038] If the safety control application designation unit 24 does not designate any of the safety control applications stored in the memory unit 23, the control unit 21 transmits input information indicated by the input signal from the input device 50 to the master device 10 via the communication unit 22, and operates the safety output circuit 26 in accordance with instructions from the master device.

[0039] According to the above configuration, the slave device 20 can also be used as a general slave device 20 that performs safety control operations in accordance with instructions from the master device 10.

[0040] Furthermore, when the safety control application designation unit 24 has not designated any of the safety control applications stored in the storage unit 23 at the time of startup of the slave device 20, the control unit 21 loads and executes the safety control application received from the master device 10 via the communication unit 22, and operates the safety output circuit 26. The control unit 21 loads and executes the safety control application received from the master device 10, and operates the safety output circuit 26 in accordance with the result determined based on the input signal obtained by the safety control application.

[0041] According to the above configuration, a safety control application can be provided from outside the slave device 20, and the slave device 20 can be made to execute safety control using the functions of the control unit 21 included in the slave device 20.

[0042] Fig. 3 is a diagram showing the hardware configuration of the control unit 21 in the slave device 20 according to an embodiment of the present invention. As shown in Fig. 3, the control unit 21 includes an interface MPU 31, an operation memory 32, and duplicated CPUs A33 and B34. CPU A33 includes a setting memory A35, and CPU B34 includes a setting memory B36. Setting memory A35 and setting memory B36 are made of non-volatile memory. CPU A33 and CPU B34 are connected to a safety input circuit 25 and a safety output circuit 26, respectively.

[0043] The interface MPU 31 is connected to the communication unit 22, the storage unit 23, and the safety control application designation unit 24, and enables the control unit 21 to exchange information with the communication unit 22, the storage unit 23, and the safety control application designation unit 24.

[0044] Returning to FIG. 2, the control unit 21 includes a communication control unit 211 , an input control unit 212 , an output control unit 213 , a safety control application selection unit 214 , a safety control application monitoring unit 215 , and a safety processing unit 216 .

[0045] The communication control unit 211 controls the communication unit 22. The communication control unit 211 has a communication function that complies with safety standards. The input control unit 212 controls the operation of the safety input circuit 25, and the output control unit 213 controls the operation of the safety output circuit 26.

[0046] The safety control application selection unit 214 stores the settings of the safety control application to be executed by the control unit 21 in the operating memory 32. When the safety control application designation unit 24 designates any one of the safety control applications stored in the storage unit 23, the safety control application selection unit 214 stores the settings of the designated safety control application in the operating memory 32.

[0047] If the number specified by the safety control application designation unit 24 is one of "1" to "14", the safety control application selection unit 214 reads the settings of the safety control application (input / output settings, safety control settings) of the specified number from the memory unit 23 and stores them in the operating memory 32.

[0048] If the number specified by the safety control application specification unit 24 is "15", the safety control application selection unit 214 stores the settings of the safety control application (input / output settings, safety control settings) received from the master device 10 via the communication unit 22 in the operating memory 32.

[0049] If the number specified by the safety control application specification unit 24 is “0”, the safety control application selection unit 214 receives only the input / output settings from the master device 10 via the communication unit 22 and stores the received input / output settings in the operating memory 32.

[0050] The safety processing section 216 is constructed by executing a safety control application stored in the operating memory 32 by the safety control application selection section 214. The safety processing section 216 includes a safety input processing section 2161, a safety output processing section 2162, and a safety control processing section 2163.

[0051] The safety input processing unit 2161 and the safety output processing unit 2162 are realized by input / output settings included in the safety control application. The safety control processing unit 2163 is realized by safety control settings included in the safety control application. The safety control processing unit 2163 is an arithmetic processing unit configured by CPU A33 and CPU B34 shown in FIG. 3 executing the safety control settings (safety control program). The CPU A33 and CPU B34 load the safety control settings stored in the operation memory 32 into the operation memory 32, perform calculations based on input signals from the safety input circuit 25, and output the calculation results to the safety output circuit 26.

[0052] The safety processing part 216 is not implemented when the safety control application is not stored in the operating memory 32. When the safety control application is not stored in the operating memory 32, the control part 21 operates the safety output circuit 26 in accordance with an instruction from the master device 10.

[0053] When the safety control application monitoring unit 215 receives an instruction from the master device 10 via the communication unit 22 to designate one of the safety control applications stored in the storage unit 23, it determines whether the safety control application designated by the master device 10 matches the safety control application designated by the safety control application designation unit 24. If they do not match, the safety control application monitoring unit 215 controls the safety output circuit 26 to stop outputting the output signal.

[0054] In this embodiment, the safety control application monitoring unit 215 receives an instruction to designate a safety control application, including a safety control application received from the master device 10 via the communication unit 22.

[0055] <Power-on procedure> Next, a description will be given of a processing procedure when the slave device 20 of this embodiment is powered on. Fig. 4 is a flowchart showing an example of a processing procedure when the slave device 20 of this embodiment is powered on.

[0056] 4, when the power supply of the slave device 20 is turned on (S1), the safety control application selection unit 214 reads the number (value) designated (selected) by the safety control application designation unit 24 (step S2). Next, the safety control application selection unit 214 determines whether or not a safety control application is stored in an area in the storage unit 23 corresponding to the read number (S3).

[0057] As described above, if the number specified by the safety control application specifying unit 24 is "1" to "14," a safety control application is stored in the storage unit 23. In this case, the safety control application selecting unit 214 determines YES in S3 and proceeds to S4.

[0058] In S4, the safety control application selection unit 214 stores the settings of the safety control application stored in the area of ​​the storage unit 23 corresponding to the read number in the operation memory 32, and starts the safety control application. As a result, a safety processing unit 216 is constructed by the safety control application stored in the storage unit 23, and the safety output circuit 26 is operated in accordance with the result obtained based on the input signal of the safety input circuit 25.

[0059] On the other hand, if the number specified by the safety control application specifying unit 24 is "0" or "15," no safety control application is stored in the area of ​​the storage unit 23 corresponding to that number. In this case, the safety control application selecting unit 214 determines NO in S3 and proceeds to S5.

[0060] In S5, the safety control application selection unit 214 starts up the slave device 20 without the safety control application. By starting up without the safety control application, the safety control application selection unit 214 enters a state of waiting for settings from the master device 10 via the communication unit 22.

[0061] When the setting waiting state is entered, the safety control application selection unit 214 repeats the process of determining whether a safety control application has been received from the master device 10 via the communication unit 22 (S6) or whether only input / output settings have been received from the master device 10 via the communication unit 22 (S7) until it determines YES for either of these.

[0062] If the answer to S6 is YES, the safety control application selection unit 214 stores the settings of the received safety control application in the operation memory 32 and starts the safety control application (S8). As a result, a safety processing unit 216 is constructed by the safety control application received from the master device 10, and the safety output circuit 26 is operated in accordance with the result obtained based on the input signal of the safety input circuit 25.

[0063] If the answer to S7 is YES, the safety control application selection unit 214 stores only the received input / output settings in the operation memory 32. The control unit 21 transmits input information indicated by the input signal of the safety input circuit 25 to the master device 10 via the communication unit 22, and operates the safety output circuit 26 in accordance with instructions from the master device 10 (S9).

[0064] <Safety control operation procedure> Next, a description will be given of a processing procedure for a safety control operation during execution of a safety control application in the slave device 20 of this embodiment. Fig. 5 is a flowchart showing an example of a processing procedure for a safety control operation in the slave device 20 of this embodiment.

[0065] 5, the safety input processing unit 2161 acquires the value of a signal from the safety input circuit 25 (S11). Next, the safety input processing unit 2161 determines whether or not an error has occurred in the self-diagnosis function (step S12).

[0066] If the determination in S12 is NO (no error has occurred), the safety input processing unit 2161 reflects the acquired input signal of the safety input circuit 25 in the input signal to be sent to the safety control processing unit 2163 (S14), and then proceeds to S15. In S15, the safety input processing unit 2161 sends the input signal to the safety control processing unit 2163.

[0067] On the other hand, if the result of S12 is YES (an error has occurred), the safety input processing unit 2161 treats the input signal of the input port terminal where the self-diagnosis function has determined that an error has occurred as OFF (FALSE), reflects the acquired input signal of the safety input circuit 25 in the input signal to be sent to the safety control processing unit 2163 (S13), and then proceeds to S15.

[0068] In S15, the safety input processing unit 2161 transmits an input signal to the safety control processing unit 2163.

[0069] The safety control processing unit 2163 acquires an input signal from the safety input processing unit 2161 (S16). The safety control processing unit 2163 performs calculations based on the input information indicated by the input signal and determines an output signal to be sent to the safety output processing unit 2162 (S17). The safety control processing unit 2163 sends the determined output signal to the safety output processing unit 2162 (S18). The safety output processing unit 2162 acquires an output signal from the safety control processing unit 2163 (S19). Next, the safety output processing unit 2162 determines whether or not an error has occurred in the self-diagnosis function (S20).

[0070] If the determination in S20 is NO (no error has occurred), the safety output processing unit 2162 reflects the acquired output signal in the input signal to be sent to the safety output circuit 26 (S22), and then proceeds to S23.

[0071] On the other hand, if the result of S20 is YES (an error has occurred), the safety output processing unit 2162 treats the output signal of the output port terminal where the self-diagnostic function has determined that an error has occurred as OFF (FALSE), reflects the acquired output signal in the output signal to be sent to the safety output circuit 26 (S21), and then proceeds to S23.

[0072] In S23, the safety output processing unit 2162 transmits an output signal to the safety output circuit 26.

[0073] <Safety control application monitoring procedure> Next, a description will be given of a processing procedure for monitoring a safety control application during execution of the safety control application in the slave device 20 of this embodiment. Fig. 6 is a flowchart showing an example of a processing procedure for monitoring a safety control application in the slave device 20 of this embodiment.

[0074] The flowchart in FIG. 6 shows the processing performed when the slave device 20 is executing any of the safety control applications stored in the memory unit 23 or a safety control application loaded from the master device 10, in accordance with the specification by the safety control application specification unit 24.

[0075] As shown in FIG. 6, while the safety processing unit 216 is operating, the safety control application monitoring unit 215 determines whether or not a signal specifying a safety control application has been received from the master device 10 via the communication unit 22 (S31).

[0076] The master device 10 transmits a signal specifying one of the safety control applications stored in the storage unit 23, or a signal specifying a safety control application transmitted from the master device 10. The signal specifying a safety control application transmitted from the master device 10 is a signal specifying an appropriate safety control application according to the connection relationship between the slave device 20 and the input device 50 and the output device 60.

[0077] If the answer to S31 is YES, the safety control application monitoring unit 215 reads the number of the safety control application specifying unit 24 (S32). Next, the safety control application monitoring unit 215 determines whether the safety control application specified by the master device 10 matches the safety application specified by the number of the safety control application specifying unit 24 (S33).

[0078] If the answer to S33 is YES, the safety control application monitoring unit 215 continues the calculation execution by the safety control processing unit 2163 (S34). While the slave device 20 is operating, the answer to S33 will be YES unless the number of the safety control application designation unit 24 is changed.

[0079] On the other hand, if the determination in S33 is NO, the safety control application monitoring unit 215 stops the execution of calculation by the safety control processing unit 2163 and stops the output of the output signal from the safety output circuit (S35). If the number of the safety control application designation unit 24 is changed while the slave device 20 is operating, the determination in S33 is NO.

[0080] The process of monitoring the safety control application in steps S31 to S35 may be performed for each execution cycle of the CPU A33 and CPU B34, for example.

[0081] As a result, safety control operations using multiple safety control applications stored in the memory unit 23 by the slave device 20 are performed under the supervision of the master device 10, thereby further improving safety.

[0082] However, such a monitoring function for the safety control application is not necessarily required. In other words, the slave device 20 can operate even when it is not connected to the master device 10. In that case, the facility manager can use the safety control application designation unit 24 to designate an appropriate safety control application according to the connection relationship between the slave device 20 and the input device 50 and output device 60.

[0083] In addition, the safety control application monitoring unit 215 may monitor a change in the number of the safety control application designation unit 24 after the slave device 20 is started, and when it detects that the number has been changed, it may control the safety output circuit 26 to stop outputting the output signal.

[0084] Furthermore, although the slave device 20 in this embodiment is illustrated as being arranged in one housing, the slave device 20 may be arranged (unit) in which each part of the slave device 20 is arranged across multiple housings that can be connected.

[0085] Furthermore, in the slave device 20 of this embodiment, the safety control application designation unit 24 is configured to designate a safety control application (including a safety control program) stored in the storage unit 23, but it may also be configured to designate an operation mode within the slave device 20. In other words, the safety control application designation unit 24 may be configured as a method for designating an operation mode in which different behaviors are performed within the slave device 20.

[0086] [Software implementation example] The functions of the slave device 20 (hereinafter referred to as the "device") can be realized by a program that causes a computer to function as the device, and a program that causes a computer to function as each control block of the device (particularly each part included in the control unit 21).

[0087] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program, thereby realizing the functions described in each of the above embodiments.

[0088] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.

[0089] Furthermore, some or all of the functions of the control blocks can be realized by logic circuits. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of the present invention. In addition, the functions of the control blocks can also be realized by, for example, a quantum computer.

[0090] Furthermore, each process described in each of the above embodiments may be executed by AI (Artificial Intelligence). In this case, the AI ​​may run on the control device or on another device (for example, an edge computer or a cloud server).

[0091] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0092] 1 Network 10 Master Device 20 Slave Device 21 Control section 22 Communications Department 23 Memory section 24 Safety control application specification section 25 Safety Input Circuit 26 Safety output circuit 50 Input Devices 60 Output Devices 211 Communication control section 212 Input control section 213 Output control section 214 Safety Control Application Selection Section 215 Safety Control Application Monitoring Unit 216 Safety Processing Department P1~P4 Input ports P5~P8 output ports

Claims

1. A slave device that is connected to a network for safety control and communicates with a master device, a communication unit for performing communication via the network; a safety input circuit having a plurality of input ports for receiving input signals from an input device; a safety output circuit having a plurality of output ports for outputting an output signal to an output device; a storage unit that stores a plurality of safety control applications, each including an algorithm that determines the output signal based on input information indicated by the input signal; a safety control application designation unit that can designate any one of the plurality of safety control applications stored in the storage unit; and a control unit, The control unit a slave device that, when the safety control application designation unit designates a safety control application stored in the storage unit, loads the safety control application from the storage unit, executes the safety control application, and operates the safety output circuit.

2. The control unit When an instruction to designate any one of the safety control applications stored in the storage unit is received from the master device via the communication unit, determining whether the safety control application designated by the master device and the safety control application designated by the safety control application designation unit match; 2. The slave device according to claim 1, wherein if they do not match, the slave device controls the safety output circuit to stop outputting the output signal.

3. The control unit If the safety control application designation unit does not designate any of the safety control applications stored in the storage unit, The slave device according to claim 1 , wherein the input information is transmitted to the master device via the communication unit, and the safety output circuit is operated in accordance with an instruction from the master device.

4. The control unit When the slave device is started, if the safety control application designation unit does not designate any of the safety control applications stored in the storage unit, The slave device according to claim 1 , wherein the slave device loads and executes the safety control application received from the master device via the communication unit, and operates the safety output circuit.

5. The slave device according to claim 1 , wherein the storage unit includes a removable storage medium that stores a plurality of the safety control applications.

6. The slave device according to claim 1 , wherein the safety control application designation unit is configured by a mechanical switch.

7. The slave device according to claim 6 , wherein the safety control application designation unit is configured to designate an operation mode of the slave device.

8. The slave device according to claim 1 , wherein each unit of the slave device is arranged across a plurality of connectable housings.

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