JPH0792900A - Programmable controller - Google Patents

Abstract

PURPOSE:To eliminate the need to alter a peripheral unit even when a CPU unit is changed to a unit having a different interface, etc. CONSTITUTION:The main body unit 1 and the peripheral unit 2 are connected, through an I/F module 3 and when a value appearing on an address bus 12 from the main body unit 1 is different from the value stored in an address register 33, data of the peripheral unit 2 are stored in a data register 33 through a port 21 with the latch signal 36 from a clock circuit 35. When the value appearing on the address bus 12 matches the value stored in the address register 33, on the other hand, a latch inhibition signal 37 is outputted from the address register 33 to a data register 34 to stop the data register 34 from latching the data of the port 21 through a peripheral I/F part 32, and at the same time the MPU 11 of the CPU unit 1 fetches the contents of the data register 34.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a programmable controller (to be referred to as a PLC hereinafter) in which a main unit and peripheral units are connected via an interface module.
Said).

[0002]

2. Description of the Related Art A conventional PLC is generally composed of a main unit having an MPU for executing a user program and peripheral units such as I / O units and communication units other than the main unit. The peripheral units are connected to each other by several ports or buses such as a data bus and an address bus.

[0003]

However, in such a conventional PLC, the interface between the main unit and the peripheral unit, such as a port or a bus, or the communication protocol thereof is dedicated to each PLC. PL
There is a problem that if C cannot be connected and the main unit is changed to one having a different interface or communication protocol, the peripheral unit must be changed at the same time.

Therefore, an object of the present invention is to provide a programmable controller which does not need to change the peripheral unit even when the main unit is changed to one having a different interface or communication protocol.

[0005]

In order to achieve the above object, in the invention described in claim 1, the main body unit and a peripheral unit having an interface different from that of the main body unit are connected via an interface module. A programmable controller, wherein the interface module has a body interface unit connected to the body unit and its interface, a peripheral interface unit connected to the peripheral unit and its interface, and an address corresponding to the peripheral unit in advance. The main body unit has a stored address storage means and an interface conversion means for converting an interface of data exchanged between the main body interface section and the peripheral interface section, and the main body unit is stored in the address storage section. Ad By specifying the scan has access means for accessing to the peripheral unit via the interface conversion unit, characterized in that.

According to a second aspect of the present invention, in the programmable controller according to the first aspect, there is provided a base unit having a slot portion to which a peripheral unit having the same interface as the main body unit is connected, and the main body unit is provided in the slot portion. When connecting peripheral units having different interfaces, the connection is made via an interface module.

According to a third aspect of the present invention, in the programmable controller according to the first aspect, an interface module is provided, and a peripheral unit having an interface different from that of the main body unit is connected to the main body unit via the interface module. A base unit having a slot portion and a base unit having no interface module and directly connected to the main body unit and having a peripheral portion having the same interface as the main body unit connected thereto. It is characterized by

According to a fourth aspect of the invention, in the programmable controller according to the first aspect, one base unit is directly connected to the main body unit, and a slot portion to which a peripheral unit having the same interface as the main body unit is connected. , And a slot portion connected to the main body unit via the interface module and to which a peripheral unit having an interface different from that of the main body unit is connected.

According to a fifth aspect of the present invention, there is provided a programmable controller in which a main body unit and a peripheral unit having an interface different from that of the main body unit are connected via an interface module, and the peripheral unit is its own unit. Interface type signal output means for outputting an interface type signal indicating the type of interface of the main body unit, a main body interface section connected by the interface, and a plurality of peripheral units having different interfaces. Are exchanged between the main body interface section and the peripheral interface section, a plurality of peripheral interface sections connected by the interface, address storage means in which addresses corresponding to the peripheral units are stored in advance, and Interface conversion means for converting the interface of the peripheral unit, and when the peripheral unit is connected to one of the plurality of peripheral interface units, receives the type signal from the type signal output means and inputs the signal according to the interface of the peripheral unit. Input / output selection means for selecting an output from the main body interface section or interface conversion means and connecting it to the peripheral interface section, and the main body unit specifies the address stored in the address storage means. It has an access means for accessing the above-mentioned peripheral unit via an interface module.

According to a sixth aspect of the invention, in the programmable controller according to the fifth aspect, the interface module is provided, and the base unit is provided with the main unit and the slot unit for connecting the peripheral unit connected via the interface module. It is characterized by having.

According to a seventh aspect of the present invention, there is provided a programmable controller in which a main body unit and a peripheral unit are connected via an interface module, wherein the main body unit and the peripheral unit are respectively
The interface module has data exchanging means for exchanging data with the other unit by different communication protocols, and the interface module stores data exchanged between the main body unit and the peripheral unit, and the data storing means. The bus usage right control means for controlling acquisition of the bus usage right necessary for accessing, and the bus usage right controlled by the bus usage right control means by the same communication protocol as the data exchange means of the main unit, And access control means for causing the data exchange means of the peripheral unit to access the data storage means when the bus use right is acquired and releasing the bus use right to the data exchange means of the main body unit at the end of the access. It is characterized by

[0012]

According to the invention described in claims 1 to 4, the main unit and the peripheral unit having an interface different from that of the main unit are connected via the interface module,
In the interface module, the interface conversion means converts the interface of data exchanged between the main body interface section and the peripheral interface section. Then, the main body unit accesses the peripheral unit via the interface conversion means by designating the address stored in the address storage means by the access means.

According to the present invention, the main body unit and the peripheral unit having an interface different from that of the main body unit are connected through the interface module, and the interface type signal output means of the peripheral unit is the interface of the own unit. An interface type signal indicating the type is output. In the interface module, when a peripheral unit is connected to one peripheral interface unit, it receives a type signal from the type signal output means, and inputs and outputs according to the interface of the peripheral unit from the main body interface unit or the interface conversion unit. Select and connect to the peripheral interface section.
Then, the main body unit accesses the peripheral unit via the interface module by designating the address stored in the address storage unit by the access unit.

According to a seventh aspect of the present invention, the main unit for exchanging data with the partner unit and the peripheral unit are connected via the interface module by different communication protocols.
The data storage means stores data between the main unit and the peripheral unit, and the bus usage right control means controls acquisition of the bus usage right required when accessing the data storage means. Then, when the access control means acquires the bus use right from the bus use right control means by the same communication protocol as the main unit, the data exchange means of the peripheral unit is made to access the data storage means, and at the end of the access, the bus use right is acquired. To the main unit.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a PLC according to the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of an embodiment (hereinafter, referred to as a first embodiment) according to the invention described in claim 1.

This PLC comprises a main unit 1 on which an MPU 11 and the like are mounted and a peripheral unit 2 such as an I / O unit.
And an interface module 3 for connecting the main unit 1 and the peripheral unit 2.

The main unit 1 accesses the data register of the interface module by designating the address stored in the address register of the interface unit, which will be described later, as the access means.
Has 1.

The interface module 3 is a main body interface section 31 connected to the main body unit 1 via a bus interface (hereinafter referred to as a bus interface).
And the interface between the peripheral unit 2 and the port (hereinafter,
A peripheral interface unit 32 connected by a port interface), an address register 33 that stores an address corresponding to the peripheral unit 1 at the time of initial processing, a main body interface unit 31 and a peripheral interface unit 3
2 is connected to the peripheral interface unit 32, stores the data from the peripheral unit 2, and converts the interface of the data exchanged between the interface units 31 and 32. The data register 34 and the data register 34 are latched. And a clock circuit 35 which sends a latch signal 36 for instructing timing.

In the figure, 12 is an address bus, 13 is a data bus, 14 is a control bus, 21 is a port,
Reference numeral 37 denotes a latch inhibit signal described later.

Next, the operation of the first embodiment will be described with reference to FIG. First, the main unit 1 and the peripheral unit 2
Are connected via the interface module 3 and the peripheral unit 2 is not in the selected state, that is, when the value appearing on the address bus 12 from the main unit 1 and the value stored in the address register 33 are different, The data of the peripheral unit 2 is taken into the data register 34 by the port interface via the port 21 and the peripheral interface section 32, and is stored in the data register 33 by the latch signal 36 from the clock circuit 35 for every fixed period.

On the other hand, when the peripheral unit 2 is selected by the MPU 11 of the main unit 1, that is, when the value appearing on the address bus 12 from the main unit 1 matches the value stored in the address register 33, the data register In order to prevent the data of 34 from changing when being taken into the main unit 1, the address register 33
Outputs a latch inhibit signal 37 to the data register 34, and the data register 34 stops latching the output of the port 21 via the peripheral interface unit 32.

Then, when the MPU 11 of the main unit 1 accesses the data register 34 via the bus interface 31 via the bus interface, the output of the peripheral unit 2 converted from the port interface to the bus interface is transferred from the data register 34 to the MPU 11. At the same time as being captured, the output of MPU 11
At 4 the bus interface is converted to a port interface and sent to the peripheral unit 2.

Therefore, according to the first embodiment, even if the main body unit 1 and the peripheral unit 2 have different interfaces, the main body unit 1 and the peripheral unit 2 can be connected through the interface module 3. , Even if the main unit is changed to one with a different interface, it is not necessary to change the peripheral unit. Here, three connection examples of the peripheral units in the first embodiment will be described including the base unit.

FIG. 2 corresponds to the invention of claim 2, and shows an example of connection when the interface module 3 is used as a unit.

That is, to the base unit 40 to which the main body unit 1 is connected, the slot portion 4 to which the peripheral unit 2a having the same bus interface as that of the main body unit 1 is connected.
0a is provided. And this slot portion 40a
While the peripheral unit 2a of the bus interface is directly connected to, the peripheral unit 2b of the port interface is connected via the interface module 3.

Therefore, according to this connection example, even in the peripheral unit 2b different from the interface of the main body unit 1,
The base unit 40 to which the main body unit 1 is connected, like the peripheral unit 2a having the same interface as the main body unit 1 through the interface module 3.
Can be connected to.

FIG. 3 shows an example of a connection corresponding to the invention of claim 3 in the case where an interface module requires a unit and an unnecessary unit is divided for each base unit.

That is, the base unit 41 to which the main unit 1 is connected is connected to the main unit 1 and the buses 12, 13 and 14 so that the peripheral unit 2a, which is the same interface as the main unit 1, is connected. The directly connected slot portion 41a is provided, and the interface module 3 is not provided.
On the other hand, the interface module 3 is connected to the base unit 42 connected to the base unit 41 via the buses 12, 13, and 14 so that a plurality of peripheral units 2b having a port interface different from the bus interface of the main body unit 1 are connected. It is provided. That is, the peripheral interface unit 32 of this interface module 3
A plurality of slot portions 42a of the port interface are provided in each slot, and the peripheral unit 2b of the port interface is connected to each slot portion 42a.

Therefore, according to this connection example, the base unit 41 to which the peripheral unit 2a not requiring the interface module 3 is connected and the base unit 42 to which the necessary peripheral unit 2b is connected can be configured separately. .

FIG. 4 corresponds to the invention described in claim 4, and one base unit 43 has a slot 43a for connecting the peripheral unit 2a which is the same bus interface as the main unit 1 and a peripheral which is a port interface. An example in which a slot 43b for connecting the unit 2b is provided is shown.

In other words, a bus interface slot 43a which is directly connected to the main unit 1 via the buses 12, 13 and 14 is connected to the single base unit 43.
A slot 43b connected to the port interface via the interface module 3 is provided.
The bus interface peripheral unit 2a is connected to the slot 43a, and the port interface peripheral unit 43b is connected to the slot 43b.

Therefore, according to this connection example, peripheral units having two different types of interfaces, that is, peripheral units 2a and 2b, can be connected to one base unit 43.

Next, an embodiment (hereinafter referred to as a second embodiment) according to the invention of claim 5 will be described.

FIG. 5 shows the configuration of the PLC of the second embodiment. It should be noted that the components having the same functions as those of the first embodiment will be described with the same reference numerals.

The PLC of the second embodiment is similar to the first embodiment in that the main body unit 1 on which the MPU 11 and the like are mounted,
Peripheral unit 2 such as I / O unit and main unit 1
And an interface module 3 for connecting the peripheral unit 2 to the peripheral unit 2. In this embodiment, while the peripheral unit 2 outputs the interface type signal 23,
The interface module 3 is configured to select the input / output according to the interface type signal 23.

That is, the peripheral unit 2 has the interface type signal output circuit 22 as the type signal output means, and when connected to the interface module 3, the interface type signal 23 indicating the type of the interface of its own unit. The interface module 3
Configured to output to.

The interface module 3 includes a main body interface section 31 and a plurality of peripheral interface sections 32 connected to a plurality of peripheral units 2 each having a different interface (only one peripheral interface section is shown in the figure for convenience). However, it is assumed that there is a plurality), the address register 33, and the data register 3
4, a clock circuit 35, and a multiplexer 38 as an input / output selection unit.

When the peripheral unit 2 is connected to one of the plurality of peripheral interface units 32, the multiplexer 38 receives the interface type signal 23 output from the interface type signal output circuit 22 and receives the interface type signal 23. The input / output corresponding to the interface is selected from the main body interface section 31 or the data register 34 and connected to the peripheral interface section 32.

Next, the operation of the second embodiment will be described with reference to the drawings. FIG. 5 shows a case where the peripheral unit 2 of the bus interface, which is the same interface as the main unit 1, is connected. In this case, when the interface module 3 and the peripheral unit 2 are connected, the peripheral unit is connected. The interface type signal output circuit 22 of No. 2 outputs the interface type signal 23 indicating the bus interface, and inputs it to the multiplexer 38 of the interface module 3.

Therefore, the multiplexer 38 includes the main body interface section 31 from the MPU 11 of the main body unit 1.
Also, direct input / output via the buses 12, 13, 14 is selected, and input / output with the peripheral interface unit 32 is performed by the bus interface.

FIG. 6 shows a port interface peripheral unit 2 which is an interface different from the main unit 1.
Is connected. In this case, the interface type signal output circuit 22 of the peripheral unit 2 outputs an interface type signal 23 indicating a port interface which is the type of the interface, and the multiplexer 38 of the interface module 3 is shown. To enter.

Therefore, the multiplexer 38 selects the input / output via the main body interface section 31 and the data register 34, that is, selects the port interface, and the port interface of the peripheral unit 2 via the peripheral interface section 32 is selected. I / O will be performed.

Therefore, according to the second embodiment, the input / output of the interface module 3 is automatically changed according to the interface such as the bus or port of the peripheral unit 2 connected to the interface module 3, which is different. The peripheral unit 2 of the interface can also be connected to the main body unit 1 through the same interface module 3, and the peripheral unit does not have to be changed even when the main body unit is changed to that of a different interface.

Here, a connection example of the peripheral units in the second embodiment is shown including the base unit.

FIG. 7 corresponds to the invention of claim 6, and shows an example in which two interface modules 3 of the second embodiment are provided in the base unit 44.

In this case, on the side of the interface module 3a to which the peripheral unit 2a of the bus interface is connected, since the interface type signal indicating the bus interface is input from the peripheral unit 2a, the multiplexer 38a inputs the signal to the peripheral unit 2a. While the output is the bus interface, on the side of the interface module 3b to which the peripheral unit 2b of the port interface is connected, since the interface type signal indicating the port interface is input from the peripheral unit 2b, the multiplexer 38b sends the peripheral unit 2b to the peripheral unit 2b. Input / output of is the port interface.

Next, an embodiment (hereinafter referred to as a third embodiment) according to the invention of claim 7 will be described.

The PLC of the third embodiment can be connected even when the main unit and the peripheral unit do not have a shared memory for exchanging data with each other and the communication protocol, that is, the bus control procedure to the shared memory is different. , Which enables data exchange.

FIG. 8 shows the configuration of the PLC of the third embodiment. In the PLC of the third embodiment, the main unit 5 and the type A peripheral unit 6a are directly connected to the system bus 8 on the base unit 7, and the main unit 5 and the type B peripheral unit 6b are connected to the base unit. 7
It is configured to be connected to the upper system bus 8 via an interface module 71 provided in the base unit 7.

The main unit 5 has an MPU 51 as a data exchange means for exchanging data by accessing a shared memory by a predetermined communication protocol.

The peripheral unit 6a is a peripheral unit dedicated to type A, that is, a main unit, and is a shared memory 61a of a single-port memory for exchanging data with the main unit 1 and a bus use right to the shared memory 61a. And a MPU as a data exchange means for accessing the shared memory 61a by acquiring the bus use right from the bus use right acquisition control circuit 62a by the same communication protocol as the MPU 51 of the main body unit 5
63a.

The peripheral unit 6b is a type B, that is, a peripheral unit having a communication protocol different from that of the main unit,
HALT / PASS described later without shared memory
It has MPU61b as a data exchange means which controls and exchanges data with MPU51 of the main body unit 5 by a communication protocol different from MPU51 of the main body unit 5.

The interface module 71 includes a shared memory 71a for storing input / output data exchanged between the main unit 5 and the peripheral unit 6b, an MPU 61b of the peripheral unit 6b, and a HALT / PAS as described later.
S control is performed, and the shared memory 71a is provided to the MPU 61b.
Access control circuit 71b as an access control means for controlling to access to MPU5 of main unit 5
1 and the access control circuit 71b, a bus use right control circuit 71c for controlling acquisition of the bus use right.

Next, the processing in this third embodiment will be described. FIG. 9 shows HALT / PASS control which is a data exchange process in the access control circuit 71b of the interface module 71 and the MPU 61b of the peripheral unit 6b in the third embodiment.

First, when the MPU 51 of the main body unit 5 finishes the access to the shared memory 71a of the interface module 71 and releases the bus use right, the access control circuit 71b then uses the bus use right control circuit 71c to access the bus. The usage right is acquired (step 101 “Yes”), and a HALT ready is output to the MPU 61b of the peripheral unit 6b (step 102). The MPU 61 receives this HALT ready (step 20).
1), it outputs a HALT request to the access control circuit 71b (step 202).

In the access control circuit 71b, the HAL
Confirm that the T request has been received (step 103 "Ye
s "), transition to the HALT state (step 104).
Therefore, the MPU 61b of the peripheral unit 2b acquires the access right to the shared memory 71a, and transmits / receives data, that is, writes the transmitted data to the shared memory 71a and reads the received data (step 203).
When the data transmission / reception is completed, the access control circuit 71
The HALT release process and the PASS set process of b are performed (step 204).

Then, the access control circuit 71b causes the HA
The LT state is released and the bus use right is released (step 105). Therefore, the bus use right is given to the MPU 51 of the main body unit 5, and in the peripheral unit service processing, the MPU 51 performs the read / write processing to the shared memory in the same method as when the peripheral unit 2a accesses.

Since the peripheral unit 6a is a peripheral unit dedicated to the main unit of type A, the bus use right is acquired from the bus use right acquisition control circuit 62a by the same communication protocol as the MPU 51 of the main unit 5. To access the shared memory 61a.

Therefore, according to the third embodiment, even if the communication protocol of the bus control procedure to the shared memory is different between the PLC main unit and the peripheral unit which do not have the shared memory for data exchange, this interface module is used. By using and connecting both units, data exchange becomes possible. Therefore, even if the main body unit is changed to one having a different communication protocol, it is not necessary to change the peripheral unit.

[0060]

As described above, according to the invention described in claims 1 to 4, the main body unit and the peripheral unit having an interface different from that of the main body unit, and the interface module having the interface section corresponding to the interface of both units are provided. By connecting via the interface and converting the data exchanged between the interface parts, it is possible to connect even if the interfaces of both units are different, and even if the main unit is changed to one with a different interface No need to change units.

According to the present invention, the main body unit and a peripheral unit having an interface different from that of the main body unit are connected through an interface module having an interface section corresponding to the interface of both units, and the peripheral unit is connected. Since the interface type signal is sent from the unit to the interface module and the interface module selects the input / output according to the interface of the peripheral unit, the input / output of the interface module is automatically performed according to the interface of the peripheral unit. It can be changed, and the peripheral unit does not have to be changed even when the main unit is changed to one with a different interface.

Further, in the invention according to claim 7, the main body unit and the peripheral unit are connected via the interface module, the data storing means of the interface module stores data between both units, and the access control means is the main body unit. Since the bus usage right is acquired by the same communication protocol as above and the peripheral unit is made to access the data storage means, the main unit and the peripheral unit that exchange data with the other unit by different communication protocols can be connected and data exchange can be performed. It will be possible. Therefore, even if the main body unit is changed to one having a different communication protocol, it is not necessary to change the peripheral unit.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a first embodiment.

FIG. 2 is an explanatory diagram showing an example of connection to a base unit in the first embodiment.

FIG. 3 is an explanatory diagram showing another example of connection to the base unit in the first embodiment.

FIG. 4 is an explanatory diagram showing another example of connection to the base unit in the first embodiment.

FIG. 5 is a block diagram showing the configuration and operation of the second embodiment.

FIG. 6 is a block diagram showing the configuration and operation of the second embodiment.

FIG. 7 is an explanatory view showing an example of connection to a base unit in the second embodiment.

FIG. 8 is a block diagram showing the configuration of a third embodiment.

FIG. 9 is a flowchart showing the operation of the third embodiment.

[Explanation of symbols]

1 Main Unit 2 Peripheral Unit 2a Peripheral Unit 2b Peripheral Unit 3 Interface Module 11 MPU (Access Unit) 22 Interface Type Signal Output Circuit (Interface Type Signal Output Unit) 31 Main Unit Interface Unit 32 Peripheral Interface Unit 33 Address Register (Address Storage Unit) 34 data register (interface conversion means) 38 multiplexer (input / output selection means) 40 base unit 41 base unit 42 base unit 43 base unit 44 base unit 51 MPU (data exchange means) 61b MPU (data exchange means) 71 interface module 71a shared Memory (data storage means) 71b Access control circuit (access control means) 71c Bus right control circuit (bus right) Control means)

Claims (7)

[Claims] 1. A programmable controller in which a main body unit and a peripheral unit having an interface different from that of the main body unit are connected via an interface module, wherein the interface module is connected to the main body unit through its interface. Between the main body interface section and the peripheral interface section, the peripheral interface section connected to the peripheral unit by the interface, the address storing means in which an address corresponding to the peripheral unit is stored in advance, and the main body interface section and the peripheral interface section. Interface conversion means for converting the interface of the data exchanged with the main body unit, and the main body unit specifies the address stored in the address storage means, and Programmable controller having an access means for accessing to the side unit, it is characterized. 2. A base unit having a slot portion to which a peripheral unit having the same interface as that of the main body unit is connected. When connecting a peripheral unit having an interface different from that of the main body unit to the slot portion, an interface module is provided. The programmable controller according to claim 1, characterized in that the programmable controller is connected through the programmable controller. 3. An interface module is provided,
A base unit that is connected to the main unit via the interface module and has a slot to which a peripheral unit having an interface different from that of the main unit is connected, and an interface module is not provided and is directly connected to the main unit. 2. The programmable controller according to claim 1, further comprising: a base unit having a slot portion to which a peripheral unit having the same interface as the main body unit is connected. 4. A base unit, which is directly connected to one main unit, to which a peripheral unit having the same interface as that of the main unit is connected, and which is connected to the main unit via an interface module. 2. The programmable controller according to claim 1, further comprising: a slot portion to which a peripheral unit having an interface different from that is connected. 5. A programmable controller in which a main body unit and a peripheral unit having an interface different from that of the main body unit are connected via an interface module, wherein the peripheral unit indicates an interface type of its own unit. The interface module has interface type signal output means for outputting an interface type signal, and the interface module is connected to each of the main body unit and a main body interface section connected by the interface, and a plurality of peripheral units having different interfaces. A plurality of peripheral interface units, address storage means in which addresses corresponding to the peripheral units are stored in advance, and an interface for data exchanged between the main body interface unit and the peripheral interface unit. And interface conversion means for converting,
When a peripheral unit is connected to one of the plurality of peripheral interface units, it receives a type signal from the type signal output unit, and selects the input / output according to the interface of the peripheral unit from the main body interface unit or the interface conversion unit. And an input / output selection unit connected to the peripheral interface unit, and the main body unit accesses the peripheral unit via the interface module by designating an address stored in the address storage unit. A programmable controller, comprising: means. 6. An interface module is provided,
The programmable controller according to claim 5, further comprising: a base unit having a slot unit for connecting a peripheral unit, which is connected to the main unit via the interface module. 7. A programmable controller configured to connect a main body unit and a peripheral unit via an interface module, wherein the main body unit and the peripheral unit exchange data with a counterpart unit by mutually different communication protocols. The interface module has a data storage means for storing data exchanged between the main unit and the peripheral unit, and a bus usage right necessary for accessing the data storage means. The bus usage right control means for controlling the acquisition and the bus usage right controlled by the bus usage right control means by the same communication protocol as the data exchange means of the main body unit are acquired. Allow the data exchange means of the unit to access the data storage means and Programmable controller bus access at Seth ends comprising an access control means for releasing the data exchange means of the main unit, characterized in that.