JPH06149319A - Method of extending input/output points of programmable controller - Google Patents

Abstract

PURPOSE:To attain the extension of a system by inhibiting the transfer of the input and output signals which are inputted to and transmitted from a signal processing circuit between an input/output unit and a programmable controller. CONSTITUTION:The input signals A-C received from a device to be controlled and extended are converted into the levels of the signals inputted to an input circuit 1. A decoder circuit 2 identifies the ON/OFF combinations shown by the signals A-C and decides the ON/OFF states of the output signals AA-EE. Thus the input signals A-C and the output signals AA-EE are newly extended. The existing input and output signals are transferred to a programmable controller but the extended input/output signals are not transferred to the programmable controller. The circuit 2 substantially carries out a sequence operation in place of the programmable controller and decides the contents of the output signals. Thus the extension of a system is attained just by extending the circuit 2 in an input/output unit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of expanding the number of input / output points of a programmable controller.

[0002]

2. Description of the Related Art Generally, a programmable controller can expand the number of input / output points of a controlled object by using an expansion unit in consideration of expansion after system installation.

[0003]

However, there is a limit to the expansion number of the input / output points of the programmable controller. This is because one is limited in the number of I / O units (units that convert I / O signals) that can be connected to the programmable controller, and second is limited in the address space that the programmable controller can use. However, as a result, the address space that can be assigned to the input / output signals is limited.

Regarding the first cause, it is possible to realize system expansion by replacing it with a large-scale programmable controller system, but this realization requires a large equipment cost. For the second cause, extension is no longer possible.

In view of the above points, the present invention provides a method for expanding the number of input / output points of a programmable controller capable of expanding the number of input / output points without significantly changing the system configuration. The purpose is to do.

[0006]

In order to achieve such an object, the present invention relates to the transfer of input / output signals exchanged between a controlled device and a programmable controller,
In a method of extending the number of input / output points of a programmable controller with an input / output unit interposed, a signal processing circuit for converting an input signal into an output signal is provided in the input / output unit, and the input signal and the output to / from the signal processing circuit are provided. The signal is not transferred between the input / output unit and the programmable controller.

[0007]

In the present invention, the extended input signal is converted into an output signal in the input / output unit without passing through the programmable controller and is transmitted in response to the controlled device.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings.

<First Embodiment> FIG. 1 shows a partial configuration of an input / output unit according to a first embodiment of the present invention.

In FIG. 1, the extended input signals A to C received from the controlled device are converted into control signal levels input to the input circuit 1. The decoding circuit 2 identifies the on / off combination indicated by the input signals A to C, and determines the on / off of the output signals AA to EE in correspondence with this combination. The output of the decoding circuit 2 is converted from the control signal level to the information transmission level by the output circuit 3 and transmitted to the controlled device.

In this embodiment, the input signals A to C and the output signals AA to EE are newly extended signals. I / O signals that have existed so far are transferred to and from the programmable controller, but extended I / O signals are not transferred to and from the programmable controller. Instead of performing the sequence operation in the programmable controller, the decoding circuit 2 substantially performs the sequence operation to determine the content of the output signal.

Therefore, even when the number of input / output points cannot be expanded on the programmable controller side, the input / output signal can be expanded by simply adding a decoding circuit in the input / output unit.

<Second Embodiment> The first embodiment is an example in which the score of the input signal is smaller than the score of the output signal, but in the opposite case, an encoding circuit is used. An example of the circuit configuration in this case is shown in FIG.

<Other Embodiments> (1) When the number of extension signal points is large, a nonvolatile memory such as E is used as a circuit for converting an input signal into an output signal.
EPROM can be used. In this case, the output of the input circuit 1 is address-inputted to the memory, and the on / off data of the memory area designated by the address is output to the output circuit 3. The memory contents are previously written in the memory by a write circuit using a DIP switch or the like. This example has an advantage that the relationship between the input signal and the output signal can be variably set.

Such a circuit may be added in an existing I / O unit or may be newly installed in an I / O unit separate from the existing I / O unit.

(2) When there is a combination of an existing input / output signal and an expanded input / output signal such as a new output signal is created using an existing input signal, the input circuit (input element) 1, It is preferable to use an output circuit (output element) 3 that can be attached to and detached from the input / output unit.

[0017]

As described above, according to the present invention, the system can be expanded even when the number of input / output signals cannot be expanded on the programmable controller side.
In addition, it is not necessary to change the configuration of the entire system for this expansion.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a circuit configuration of a second embodiment of the present invention.

[Explanation of symbols]

 1 input circuit 2 decoding circuit 3 output circuit 4 encoding circuit

Claims (1)

[Claims] 1. A signal for converting an input signal into an output signal in a method of expanding the number of input / output points of a programmable controller with an input / output unit interposed when transferring an input / output signal exchanged between a controlled device and a programmable controller. A processing controller is provided in the input / output unit, and the input signal and the output signal input to and output from the signal processing circuit are not transferred between the input / output unit and the programmable controller. How to expand the number of I / O points.