JP2001219797A - Control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device that can flexibly respond to the number of input/output apparatuses to be connected, has good expansion property, and is economical. SOLUTION: A control unit 1 comprises a power supply unit 11, a body unit 12, and input/output units 13. The plurality of input/output units 13 having a common hardware structure are interconnected in a daisy-chain shape in response to the number of input/output apparatuses to be connected, and logic circuits of PLD (PLCD1, PLCD2) of the interconnected units are programmed according to specifications of the input/output apparatuses to be connected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a control device,
For example, the present invention relates to a control device mounted on a moving body such as an automobile and performing various controls on the moving body.

[0002]

2. Description of the Related Art Conventionally, in the field of control devices to which computer technology is applied, processing for controlling a predetermined actuator in accordance with various sensor output signals input from the outside has been widely performed.

In such a control device, it is necessary to connect to an external sensor or actuator via a predetermined input / output interface. For this reason, when preparing a plurality of types of input / output interfaces corresponding to various specifications of the external device to be connected, or when connecting a plurality of external devices via a communication line, the specifications of the communication line to be adopted Due to the above limitations, the number of connectable external devices may need to be considered.

[0004]

In recent years, in the field of automobiles, which are typical moving bodies, navigation systems, driving support systems, or ITS (Intellige
nt Transport Systems) and other control systems have been developed and are being put to practical use.However, since these systems are not installed in all vehicles at once,
Generally, it is expected that dedicated control devices for realizing those systems will be individually mounted.

[0005] However, it is difficult to mount a plurality of dedicated control devices in a vehicle having a limited storage space, and it is burdensome for a user to purchase several types of control devices. One control system
There is a demand for a control device that has performance that can be realized by one control device and that is excellent in expandability and economy.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control device which can flexibly cope with the number of input / output devices to be connected and which is excellent in expandability and economy.

[0007]

To achieve the above object, a control device according to the present invention has the following configuration.

That is, at least one input / output unit that can be connected in a daisy chain using a first communication cable, and the second communication cable is connected to the input / output unit via a second communication cable. And a control unit for performing a predetermined control operation in accordance with input data input through the second communication cable and transmitting control output data corresponding to the operation result to the second communication cable.

Preferably, the input / output unit includes a PLD capable of programming a desired logic circuit, and a plurality of types of input / output circuits capable of transferring data with the PLD according to the logic circuit programmed in the PLD. And the PLD
A bidirectional buffer for controlling a data transfer direction to the arithmetic and control unit in accordance with a logic circuit programmed in the first and second communication cables; It is preferable to include a connector and a second connector capable of connecting the bidirectional buffer and the PLD to the first communication cable.

[0010] In this case, preferably, in a default state, the bidirectional buffer transfers data input from the first or second communication cable via the first connector to the PLD and the second connector. When the plurality of input / output units are connected in a daisy chain, the control output data sent from the arithmetic and control unit to the second communication cable is controlled by the plurality of input / output units. It is good to be transmitted to an output unit almost simultaneously.

Further, for example, when the PLD is given an individual identification number in advance, and the control output data sent from the arithmetic and control unit includes the identification number data for specifying the PLD, The PLD
Preferably, the data transfer direction of the bidirectional buffer is controlled according to the identification number data input via the first connector.

Also, for example, a connector provided at an end of the first communication cable, which is connected to the first or second connector, is connected to the first or second connector. It is preferable that the input / output unit is housed in a state in which the input / output unit is in contact with the inner surface.

[0013]

According to the present invention, it is possible to provide a control device which can flexibly correspond to the number of input / output devices to be connected and which is excellent in expandability and economy.

That is, according to the first aspect of the present invention, by connecting the required number of input / output units having a common hardware configuration according to the number of input / output devices to be connected, expandability and economy can be improved. This makes it possible to realize a control device that is excellent in quality.

Further, according to the second aspect of the present invention, it is possible to flexibly cope with various specifications of input / output devices to be connected.

According to the third to sixth aspects, the data transfer between the control operation unit and the plurality of input / output units can be realized by a simple circuit configuration.

Further, according to the present invention, even when the first or second connector does not have a lock mechanism, it is possible to reliably prevent the connector from falling off due to vibration.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a control device according to the present invention will be described in detail with reference to the drawings.

First, the overall configuration of a control unit (control device) according to the present embodiment will be described with reference to FIGS.

FIG. 1 is a simplified perspective view showing the overall configuration of a control unit according to this embodiment.
Is a power supply unit 11 for supplying power, a main unit 12 for performing arithmetic control of the control unit, and an input / output (I / O) for controlling input / output with various sensors and actuators.
/ O) Unit 13 has a stacked shape.

FIG. 2 is a block diagram showing the overall configuration of the control unit in this embodiment.

In FIG. 1, a power supply unit 11 converts a DC voltage supplied from an external power supply line (not shown) (for example, a vehicle battery) into a predetermined voltage for driving the main unit 12 and the input / output unit 13. It has a function as a general power supply module such as a DC converter and a circuit for monitoring or stabilizing the output voltage of the DC-DC converter, and supplies power to the main unit 12 and the input / output unit 13. In addition, the power supply unit 11 includes a hard disk device (hereinafter, HDD) as a large-capacity storage device due to storage space.

Next, the main unit 12 includes a motherboard 12A and an expansion board 12B.

The motherboard 12A is started up by the CPU 12C executing a program stored in the boot ROM in advance, and thereafter, the RAM (in the present embodiment,
While using the SIMM type as a temporary storage area, the CPU 12C executes an OS (operation system) program, an application program, and the like stored in advance in an HDD or the like in the power supply device 11.

The motherboard 12A has an integrated drive (IDE) as an input / output interface with the outside.
e Electronics) Extended Interface and PCI (Periphe
ralComponent Interconnect) interface, a media driver that reads and writes a predetermined portable storage medium,
PC that reads and writes certain PC cards such as CMCIA
A card interface and a twisted pair driver for performing communication using a twisted pair line are provided, and an input / output connector for connecting to an input / output unit 13 described later is provided. PCI memory controller and P
This is done via the CI_TO_ISA bridge.

The configuration of the various input / output interfaces provided on the motherboard 12A shown in FIG. 2 is merely an example, and is not limited to this device configuration. To implement the control device according to the present embodiment, at least It suffices if an input / output connector for connecting to the output unit 13 is provided.

The above-described functional configuration of the motherboard 12A basically has a functional configuration of a so-called board computer that is common at present, and a detailed description of each block in the present embodiment will be omitted. However, as a feature of the circuit configuration of the motherboard 12A in the present embodiment, S
A flash memory is mounted on at least one of the plurality of memory cards mounted in the IMM socket.
As a part of the main storage area of the PU 12C, it is managed in common with other memory cards. Therefore, the OS program, the application program, and the identification number (address) of each unit are stored in the address area of the flash memory.
Are stored in advance and the address area of the flash memory is referred to when the boot ROM starts up, so that when the power supply from the power supply unit 11 is started, the control unit 1 The execution of the function can be started in a short time as compared with the startup using a general hard disk.

The expansion board 12B is connected to the motherboard 12A.
PCI_TO connected to a PCI extension interface
_ISA bridge, and a plurality of types of external communication interfaces connected to the bridge module. In the present embodiment, IEEE 1394, USB (Universal) are used as the plurality of types of external communication interfaces.
ai Serial Bus), CAN (Controller Area Network),
Alternatively, each controller of the industrial network is provided, and maintenance equipment of the control unit 1 and external equipment for realizing various functions are connected to these external communication interfaces.

The extension board 12B includes an NVRAM for storing sensor data, control output data, system setting data, and the like.

The input / output unit 13 is an interface board to which sensors and actuators are connected, and the number of input / output points (sensors and sensors) required for a control system in which the above-described main unit 12 is a main unit that controls the entire system. Depending on the number of actuators), a plurality can be connected in a daisy chain (details will be described later).

<Input / Output Unit 13> Here, the features of the input / output unit 13 in the present embodiment will be described in detail.

(Hardware Configuration) FIG. 3 is a block diagram showing a hardware configuration of the input / output unit 13 in the present embodiment.

As shown in FIG.
Are two PLDs (Prog
rammable Logic Device). A PLD is a variable logic circuit element that can program a logic circuit to be executed in a digital circuit. In the present embodiment, a CPLD (Complex Programmable Logic Device) is used as an example, but an FPGA (Field Programmable Gate Array) or the like is used. You may. Note that PLCD1 and PLCD2 are
They are connected by a communication bus, and can coordinate the operation timing as needed (specifically, according to the logic circuits programmed in the PLCD 1 and the PLCD 2).

The input / output unit 13 has an A / D converter 131 for converting an analog signal output from an external sensor into digital data, and converts digital data transferred from the motherboard 12A into an analog signal and outputs the analog signal. D / A converter 13 that outputs to the actuator
2. a comparison circuit 133 for comparing sensor output signals; an input circuit 13 for performing switch signal and binary level serial communication
4. an output driver 135 for driving the actuator;
A bidirectional digital buffer 136 for switching the input / output state of digital data with an external device such as a console computer is provided. The plurality of types of input / output circuits and two PLDs (PLCD1, PLCD2) are connected to a control bus. Are connected on the substrate.

The input / output unit 13 includes a motherboard 1
A board-side connector 13B to which a cable-side connector 14B for transmitting / receiving data to / from the PCI_TO_ISA bridge of 2A or transmitting / receiving data to / from another (upstream) input / output unit 13 is connected to another (downstream) Board-side connector 13C to which cable-side connector 14C for transmitting and receiving data to and from input / output unit 13 is connected
Are provided.

The bidirectional digital buffer 137 is
A buffer whose input / output state is switched under the control of the PLCD1 and / or PLCD2, and through this buffer, the board-side connector 13B and the PLCD1 and PL
The CD2 is connected on the board by an address / control data bus, and the PLCD1 and PLCD2 and the board-side connector 13C are connected on the board by the address / control data bus.

Further, on the back side of the input / output unit 13,
In FIG. 3, a board-side connector 13B and a board-side connector 13C, not shown, are provided at target positions on the front side, and a daisy-chain connection described later by the plurality of input / output units 13 is realized.

The hardware of the input / output unit 13 shown in FIG. 3 is common hardware even when a plurality of units are used, and the function to be realized by each input / output unit 13 is two PLDs. (PLCD1,
This is realized by a logic circuit programmed in advance in the PLCD 2). Therefore, each input / output unit 13 has
Although a plurality of types (six types in this embodiment) of the above-described input / output circuits are physically all provided, a circuit that does not actually function depending on a logic circuit programmed in the PLD (that is, a connection in terms of software). Some circuits are not in the state of being performed.

The logic circuit written in the two PLDs can be written in a HDL (Hardware Description Ladder) which is a predetermined programming language by a designer using a predetermined programming device.
nguage), but the PL
The function D itself is currently common, and a description thereof will be omitted.

Next, a case where a plurality of input / output units 13 having the above-mentioned common hardware configuration are connected in a daisy chain will be described.

FIG. 4 is a conceptual diagram illustrating a state in which three input / output units 13 are connected to the motherboard 12A. A board-side connector 13B and a board-side connector 13B provided on the front and back surfaces of the board of the input / output unit 13 are shown. By the connector 13C,
This shows a state in which three input / output units 13 are connected in a daisy chain.

FIG. 5 is a diagram showing a connection state of hardware when three input / output units 13 are connected to the motherboard 12A, and corresponds to the state illustrated in FIG.

The connection cable 14 is provided with a cable-side connector 14B or a cable-side connector 14C, and these connectors are connected to the board-side connector 13B or the board-side connector 13C of the input / output unit 13 so that 5 connection states are realized.

The connection cable 14 includes signal lines corresponding to the address / control data bus. Also, two PLDs provided on each input / output unit 13
(PLCD1, PLCD2) are given addresses (identification numbers) in advance, and the CPU of the motherboard 12A
12C refers to a predetermined memory area in which a table of the address is stored, and thereby,
D can be specified by the address.

On the other hand, the input / output unit 13 and its PLD
Also, the addresses of the own unit and the own PLD are stored in a predetermined memory area, and when the address data received from the CPU 12C matches the address stored in advance, it is recognized that the own PLD is designated. be able to.

Here, as an example, in the relationship between the input / output unit 13 and the CPU 12C which can be specified by the address data as described above, for example, the CPU 12C determines whether the input / output unit 2 of the three input / output units 13 shown in FIG.
A case where sensor output data is obtained from the LCD 1 will be described.

An analog output signal of a certain sensor connected to the input / output unit 2 is converted into digital data as sensor output data by an A / D converter 131 and then converted to a digital signal.
It is stored in a storage area (not shown) of the CD1. Updating of the data in the storage area can be performed in accordance with a predetermined scan cycle of the sensor, regardless of the control of the CPU 12C of the motherboard 12A.

When the CPU 12C obtains the sensor output data which is appropriately updated as described above, the CPU 12C
First, address data specifying the PLCD 1 of the input / output unit 2 and a predetermined control signal for outputting sensor output data are sent to the connection cable 14. At this time,
Since the switching direction of the digital buffer 137 included in each input / output unit 13 is the direction from the outside to the inside of the unit (the default state), the address data and control signal transmitted to the connection cable 14 are:
The three input / output units 13 via the digital buffer 137 and the address / control data bus of each unit
Are transferred almost simultaneously to all PLDs.

At this time, the PLCD 1 of the input / output unit 1
And the PLCD 2 receive the address data and the control signal at substantially the same timing, but since the received address data does not match its own pre-stored address data, the operation corresponding to the control signal is performed. However, by referring to the address data and the control signal, it is possible to recognize that the sensor output data is transmitted from the input / output unit downstream from the own device, so that the switching direction of the digital buffer 137 of the input / output unit 1 is changed. In the direction “from inside to outside” of the unit. Then, in this case, when the transmission of the sensor output data is completed, the switching direction of the digital buffer 137 of the input / output unit 1 is switched to the default “outside to inside” direction.

The PLCD 1 and PLCD 2 of the input / output unit 3 receive the address data and the control signal at substantially the same timing, but the received address data does not match its own pre-stored address data. Therefore, the operation corresponding to the control signal is not performed, and by referring to the address data and the control signal, it is possible to recognize that the sensor output data is transmitted from the input / output unit upstream of the own device. The switching direction of the digital buffer 137 of the input / output unit 3 is kept at the default of “from outside to inside”.

The PLCD 2 of the input / output unit 2
Receives the address data and the control signal at substantially the same timing, but the received address data does not match the address data stored in advance, so that the operation corresponding to the control signal is not performed. One P
When the LCD 1 receives the address data and the control signal at substantially the same timing as another PLD, the received address data matches the address data stored in advance, so that the operation corresponding to the control signal is performed. The switching direction of the digital buffer 137 of the input / output unit 2 is switched from “inside to outside” of the unit, and the sensor output data stored in a predetermined storage area is transmitted to the connection cable 14. Then, in this case, when the transmission of the sensor output data is completed, the switching direction of the digital buffer 137 of the input / output unit 2 is switched to the default “outside to inside” direction.

According to such a procedure, the motherboard 12
The CPU 12C of A obtains the sensor output data. Although the above-described example is a case of sensor output data, transmission and reception of various data are performed between the CPU 12C of the motherboard 12A and the plurality of input / output units 13 by a similar procedure using an address (identification number). For this reason, as shown in FIG. 5, a desired number of common input / output units 13 are connected in a daisy chain as hardware, and for data transfer, addresses (identification numbers) of PLDs provided on those units are used. , An arbitrary system scale can be realized.

Next, a plurality of input / output units 13 are
The structure adopted in this embodiment for stacking and connecting in the vertical direction as shown in FIG.

FIG. 6 is a top view showing a schematic structure of the input / output unit 13 in this embodiment (note that the substrate 13D is not shown).
Is omitted.) FIG. 7 is a schematic cross-sectional view showing an internal state in a state where the two input / output units 13 are superimposed. FIG. 7 shows a state where the two input / output units 13 are connected in the AA cross section shown in FIG. Show.

As shown in FIG. 6, the chassis 13A has an outer frame shape of the input / output unit 13. In this embodiment, a lightweight aluminum material having excellent heat dissipation is employed. A board 13D to which the board-side connector 13B and the board-side connector 13C are mounted is mounted on the inner surface of the chassis 13A by screwing or the like. However, the daisy-chain connection described above with reference to FIGS. Prior to mounting the individual substrates 13D, the cable-side connector 14 of the cable 14 as shown in FIG.
B and the cable-side connector 14C are connected, and the individual boards 13D are mounted in this state. Then, in the mounted state, the cable-side connector 14B and the cable-side connector 14C of the cable 14 connected to the board 13D are fixed in a state of contacting one inner side surface of the chassis 13A as shown in FIGS. . As a result, it is possible to adopt a connector without a locking mechanism for preventing falling off,
The area of the input / output unit 13 can be minimized, and the cable 14 can be prevented from falling off even when vibration or impact is applied to the control unit 1 in the operating state.

In this embodiment, the type in which the cables are connected to the cable-side connector 14B and the cable-side connector 14C in a direction perpendicular to the connection direction of the connectors is adopted. However, the present invention is not limited to this type. Even when a type in which a cable is connected in parallel with the connection direction of the connector is employed, the same effect of preventing dropping can be enjoyed.

(Logic Circuit Inside PLD) Next, a description will be given of features of a logic circuit which is programmed as necessary in the PLD of the input / output unit 13 having the above-described features.

FIG. 8 is a block diagram showing a configuration of a process of sharing a control logic counter in the PLD of the input / output unit 13. As an example, a circuit in a case where various sensor outputs of an automobile are obtained using the input / output unit 13. An example is shown.

When the control unit according to the present embodiment is used as an on-vehicle control device, it is generally necessary to detect output signals of various sensors having greatly different detection periods. Therefore, in the present embodiment, P
In order to generate a plurality of different predetermined signals for counting a plurality of types of detection periods to be handled in the LD (PLCD1 or PLCD2), a plurality of counters counting at the plurality of types of detection periods and an oscillation at a predetermined basic frequency And a common basic period counter for counting the period that is the greatest common divisor of each period. By programming such a logic circuit, the overflow signal can be shared as one unit time, so that a predetermined amount of logic resources predetermined as PLD specifications can be used efficiently.

FIG. 9 is a block diagram showing a configuration of serial communication input processing from a plurality of types of sensors in the PLD of the input / output unit 13. As an example, various sensor outputs of a vehicle are obtained using the input / output unit 13. An example of a circuit in the case of performing this is shown. FIG. 10 is a time chart for explaining the serial communication input processing shown in FIG.

When the control unit according to this embodiment is used as a vehicle-mounted control device, it is generally necessary to detect asynchronous serial output signals of various sensors having greatly different specifications. Therefore, in the present embodiment, an idle detector in which a predetermined time of a unit of several milliseconds is set in advance monitors an asynchronous serial output signal (data) received from the sensor, and an idle period included in a serial data group output sequentially. By detecting Ti, a break of the serial output signal to be detected is detected. And the detected 1
The serial output signals of the group are converted into a parallel data format by a serial / parallel converter, and then stored in a predetermined memory area. If one set of such a logic circuit is prepared for one sensor, it is possible to easily cope with serial output signals of various sensors.

<Hardware of Main Unit 12> Next, features of the hardware of the main unit 12 in this embodiment will be described.

FIG. 11 is a diagram showing a mounting state of the main unit 12 in this embodiment.

As shown in the figure, on the upper surface of the motherboard 12A of the main unit 12, an aluminum heat radiator for guiding heat generated in the operating CPU 12C, the cache 12D, etc. to the chassis 12H via a heat radiating sheet 12E. Board 1
2F is provided to realize efficient heat radiation when the control unit 1 is used in a substantially closed state. Also, the chassis 12 to which the end of the heat sink 12F is screwed.
Since a stay mounting hole 12G is provided on the side surface of H, if the stay mounting hole is used to mount to a supporting member (for example, the body of an automobile) with a metal stay such as aluminum, better heat radiation can be achieved. Can be realized.

As described above, according to the above-described embodiment, the input / output units 13 are connected in a daisy chain in accordance with the number of input / output devices to be connected, and the PLD logic circuits of the connected units are connected. By programming according to the specification of the input / output device to be connected, it is possible to flexibly cope with various control systems, realize excellent expandability, and as a hardware, a common input / output unit 13 is used. Excellent economic efficiency can be realized by the mass production effect.

<Modification of Embodiment> Next, a modification of the above-described embodiment relating to heat radiation will be described.

FIG. 12 is a view for explaining a heat radiation structure as a modification of the present embodiment, and shows a case where a more aggressive heat radiation is performed without using a closed structure as the control unit 1.

That is, in this modification, the input / output unit 13
The power supply unit 11 is provided with an exhaust fan 11A, and the partition plate of each unit is provided with a vent hole. At this time, the position of the ventilation hole is as shown in FIG.
2, two adjacent units are provided at different positions in the horizontal direction. Thereby, convection of air from the input / output unit 13 having the smallest heat generation toward the power supply unit 11 having the largest heat generation can be caused, so that effective exhaust heat is realized.

Incidentally, the positive heat dissipation structure using the exhaust fan 11A when the control unit 1 is operated may be provided only in the power supply unit 11 if necessary.

In the above-described embodiment and its modifications, the control unit 1 is described as including the power supply unit 11. However, when the necessary power supply can be directly received from the outside, The control unit may be configured by the main unit 12 and the required number of input / output units 13.

[Brief description of the drawings]

FIG. 1 is a simplified perspective view showing the overall configuration of a control unit according to the present embodiment.

FIG. 2 is a block diagram illustrating an overall configuration of a control unit according to the present embodiment.

FIG. 3 is a block diagram illustrating a hardware configuration of an input / output unit 13 according to the present embodiment.

FIG. 4 shows three input / output units 1 on a motherboard 12A.
FIG. 3 is a conceptual diagram illustrating a state where 3 is connected.

FIG. 5 shows three input / output units 1 on a motherboard 12A.
FIG. 3 is a diagram showing a connection state of hardware when 3 is connected.

FIG. 6 is a top view showing a schematic structure of an input / output unit 13 in the embodiment.

FIG. 7 is a schematic sectional view showing an internal state in a state where two input / output units 13 are superimposed.

FIG. 8 is a block diagram illustrating a configuration of a sharing process of a control logic counter in the PLD of the input / output unit 13.

FIG. 9 is a block diagram illustrating a configuration of serial communication input processing from a plurality of types of sensors in the PLD of the input / output unit 13.

FIG. 10 is a time chart illustrating the serial communication input processing shown in FIG. 9;

FIG. 11 is a diagram showing a mounting state of the main unit 12 in the embodiment.

FIG. 12 is a diagram illustrating a heat dissipation structure as a modification of the present embodiment.

[Explanation of symbols]

 1: control unit, 11: power supply unit, 12: main unit, 12A: motherboard, 12B: expansion board, 12C: CPU, 12F: heat sink, 13: input / output unit, 13B, 13C: board side connector, 14B, 14C : Cable side connector, 14: Cable, 131: A / D converter, 132: D / A converter, 133: Comparison circuit, 134: Input circuit, 135: Output driver, 136, 137: Bidirectional digital buffer,

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenji Kamijo 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima F-term in Mazda Co., Ltd. (reference) 5B014 EB01 FA16 FB03 GA26 GC06 GD16 GD19 GD32 GD48 GE04 GE05 HC01 HC13 5B061 FF07 FF23 GG01 5H004 GA33 GA34 GA40 GB12 MA06 MA29 MA30 MA39 MA41 MA52 MA58 MA60

Claims (7)

[Claims] 1. An at least one input / output unit connectable in a daisy chain using a first communication cable; and a second communication cable connected to the input / output unit via a second communication cable. And a control unit for performing a predetermined control operation in accordance with input data input through the second communication cable and transmitting control output data in accordance with the operation result to the second communication cable. Control device. 2. The I / O unit comprises: a PLD capable of programming a desired logic circuit; and a plurality of types of I / O circuits capable of transferring data with the PLD according to the logic circuit programmed in the PLD. A bidirectional buffer that controls a data transfer direction to the arithmetic and control unit in accordance with a logic circuit programmed in the PLD; and a bidirectional buffer that can be connected to the first or second communication cable. The control device according to claim 1, further comprising: a first connector; and a second connector capable of connecting the bidirectional buffer and the PLD to the first communication cable. 3. The bidirectional buffer, in a default state, transmits data input from the first or second communication cable via the first connector to the PL.
D and control output data transmitted to the second communication cable by the arithmetic and control unit when the plurality of input / output units are connected in a daisy chain. 3. The control device according to claim 2, wherein the data is transferred to the plurality of input / output units at substantially the same time. 4. The input / output unit and the PLD are provided with individual identification numbers in advance, and control output data sent from the arithmetic and control unit includes identification number data for specifying the PLD. 4. The PLD according to claim 2, wherein the PLD controls a data transfer direction of the bidirectional buffer according to the identification number data input via the first connector. Control device. 5. The PLD, when the input identification number data represents an identification number of the own PLD, and the control output data indicates that data transmission from the own PLD is instructed. The control state of the bidirectional buffer is
The control device according to claim 4, wherein the switching is performed in a direction in which data can be transmitted from the first connector. 6. The PLD transmits data from the input / output unit when the input identification number data indicates a PLD on another input / output unit connected downstream which is different from the own PLD. 5. The control device according to claim 4, wherein when the control output data indicates that the instruction is given, the control state of the bidirectional buffer is switched to a direction in which data can be transmitted from the first connector. 7. A connector provided at an end of the first communication cable, which is connected to the first or second connector, is connected to the first or second connector, The control device according to claim 1, wherein the control device is housed in a state of being in contact with an inner surface of the input / output unit.