RS232 Read Input instability

[Stephen1234]

I have a problem regarding reading input channels on a T40H PLC.

Periodically, I receive anomalies regarding Read Input requests via RS232
e.g. I am forcing 7 inputs high on CH00 and the comms are?
Tx @01RI0000*
Rx @01RI7F00*
?as expected, however occasionally I will receive?
Rx @01RI0000*
?with the inputs still high (i.e. green LED's on).
I?m polling the request approximately 0.2 seconds and the Rx is either the correct expected value or 00.

I?m not entirely sure what?s happening here, and I?m wondering if you can shed some light on the issue.

Q:
- Have you experienced this issue before?
- Could it be voltage or current instability on one/all the inputs?
- Could it be an EMC issue?

Thanks

[support]

What voltage did you apply to the input?

If the PLC 1-7 inputs are high, you should receive the following response string:

    @01RI7F2B*   and not    @01RI7F00*

If the PLC 1-8 are OFF, you should receive the following response string:

   @01RI005A*  and not @01RI0000* as you have said.

So it appear what you have received doesn't seem like response from the PLC?