JPH1195814A - Signal transmitting method for programmable controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent waveform distortion due to module extraction from being generated and to raise the limitation to the length of a base board by detecting an unconnected module and looping back the signal transmission line of the base board in front of the detected module. SOLUTION: Extraction of modules 2-1 to 1-3 is detected from changes of bits of bit signals 6-1 to 6-3 indicating whether or not the modules are present. Namely, the module 2-2 is extracted from the base board 1, a bypass driver 5-2 is closed, and a bypass driver 8-2 is opened to bypass the signal transmission line by the bypass driver 8-2. When all the modules 2-1 to 2-3 are mounted on the base board 1, bypass drivers 5-1 and 5-2 are opened to pass input signals from the modules 2-1 and 2-2 on the signal transmission line. The bypass drivers 8-1 to 8-3 are closed to pave an arrangement where a bypass signal system is not formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal transmission method for a programmable controller for automatically controlling electronic equipment.

[0002]

2. Description of the Related Art Programmable controllers are known as devices which can automatically control electronic devices and can freely program the control contents. The programmable controller mainly includes a CPU module, an I / O module, and a base board. The CPU module executes a sequence program, that is, a program that defines contents for controlling the electronic device. The I / O module performs signal level conversion. A signal input to the CPU module from the electronic device to be controlled, for example, a signal indicating the ON / OFF state of the relay is converted into a signal level that can be processed by the CPU module, and a signal output to the electronic device to be controlled. For example, a signal for instructing ON / OFF of a relay is level-converted into a signal for long-distance transmission.

[0003] A CPU module and a plurality of I / O modules are inserted into a base board by connectors.
A signal is transmitted between the PU module and the plurality of I / O modules. Hereinafter, a CPU module and an I / O module are collectively referred to as a module unless a special distinction is required. FIG. 1 shows the configuration of this base board.

In FIG. 1, a serial signal transmission line 4 is provided on a base board 1, and a module 2 is connected to the serial signal transmission line 4 by a connector 3.

[0005]

The number of modules 2 detachably connected to the base board 1 is reduced (modules are omitted).
For example, the number of connections may decrease. In order to minimize the waveform distortion of the transmission signal on the serial signal transmission line 4, the length of the serial signal transmission line 4 has to be as short as possible.

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide a signal transmission method for a programmable controller which does not cause a waveform distortion due to a missing module and can reduce the length limitation of a base board. It is in.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, a plurality of modules are detachably connected to a base board and are connected via a signal transmission line of the base board. In a signal transmission method of a programmable controller for transmitting a signal to and from a plurality of modules, an unconnected module is detected, and the signal path is looped back before the detected module.

[0008]

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

(First Embodiment) FIG. 2 shows a configuration of a signal path of a base board 1 according to a first embodiment. 2, the same parts as those in the conventional example of FIG. 1 are denoted by the same reference numerals.
In this embodiment, a bit signal 6 indicating the presence or absence of a module is provided.
The omission of each module is detected by the change of the bits -1 to 6-3 (change of L and H). All modules 2-1
When 2-3 are mounted on the base board 1,
The bypass drivers 5-1 and 5-2 are opened, and pass the input signal signals from the modules 2-1 and 2-2 on the signal transmission path 4. On the other hand, the bypass drivers 8-1 to 8-3
Is closed, and a bypass signal system is not formed.

In such a state, for example, when the module 2-2 is removed from the base board 1, the bypass driver 5-2 is closed, the bypass driver 8-2 is opened, and the bypass driver 8-2 is opened. The signal transmission path 4 is bypassed. Thus, for example, module 2
The input signal from -1 passes through the bypass driver 8-2 and is transmitted on the signal transmission path 4. In this example, even if the module 2-3 on the downstream side of the signal transmission path 4 is mounted on the baseboard 1, the module 2-1 on the upstream side,
If any of 2-2 is removed from the base board 1, no signal is transmitted.

(Second Embodiment) FIG. 3 shows a bypass configuration of a second embodiment. In FIG. 3, 5-1 to 5-6,
8-1 and 8-2 are bypass drivers;
-2 is a gate. In this example, when one of the modules in a predetermined number of units (three in this example) is pulled out, the corresponding bypass driver is operated to loop the signal transmission path 4.

For example, when the module 2-5 is pulled out, the bypass drivers 5-5 and 8-2 operate, and the signals to the modules 2-4 to 2-6 are changed by the formation of the bypass by the bypass driver 8-2. Will not be transmitted. This example has an advantage that it is not necessary to provide the driver (8-1, 8-2) for each module.

(Third Embodiment) In the above embodiment, when a certain module is pulled out, no signal is transferred to the downstream module. However, no matter which module is pulled out, the signal is transferred to the next module, and all signals are transferred. FIG. 4 shows a bypass configuration according to the third embodiment in which a loop-back is performed when the module is pulled out. In FIG.
-1, 5-2, 10-1, and 10-2 are bypass drivers, 11 to 14 are gates, and when all modules after module 2-1 are pulled out, bypass is performed by the bypass driver 10-1. Formed and Module 2
Bypass driver 10-2 forms a bypass when all the modules after -2 are pulled out. For this reason. There is no limit on the length of the baseboard, which increases design flexibility.

[0014]

As described above, according to the first aspect of the present invention, the signal transmission line loops back in front of the extracted module, so that the signal waveform is not deformed due to the extraction of the module, and the signal transmission is prevented. Road reliability is increased.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a signal path of a conventional base board.

FIG. 2 is a circuit diagram illustrating a configuration of a signal path of a base board according to the first embodiment.

FIG. 3 is a circuit diagram illustrating a configuration of a signal path of a base board according to a second embodiment.

FIG. 4 is a circuit diagram showing a configuration of a signal path of a base board according to a third embodiment.

[Explanation of symbols]

 1 base board 2 module 3 connector 4 (serial) signal transmission path

Claims (1)

[Claims] 1. A signal transmission method for a programmable controller, wherein a plurality of modules are detachably connected to a base board, and a signal is transmitted to and from the plurality of modules via a signal transmission path of the base board. A signal transmission method for a programmable controller, comprising detecting an unconnected module and looping back the signal path before the detected module.