OMRON CPM2A PLC and RS-232C to the PC

[vislab]

Hello,

I hope someone can help to resolve the current issue that I have now. I am using OMRON CPM2A PLC connected to the desktop PC so that it is able to communicate through the RS-232C COM port.
And I wrote a simple PLC code which uses 2 PLC outputs to operate a simple pneumatic solenoid valves so it just works fine.
Here I also wrote a simple VB code to send "OK" signal to the PLC through the RS-232C COM port so the PLC routine is supposed to run only if it receives "OK" signal from the PC through the RS-232C COM port. I used of course RXD PLC function in the PLC code. So right now there is only one direction communication from the PC to the PLC.

But the problem I saw is this everytime after I shutdown the desktop PC and reboot it, the PLC would not run anymore it means when it receives "OK" signal it did not do anything so no output LEDs lit on. And also when the PC shuts down if I look at the PLC panel there was a COMM LED blinking once.

But if I unplug the power to the PLC and plug it back then it runs OK again. So far I don't know what is wrong and what I can do to fix this problem but it is weird everytime when I just reboot not shutdown then it still works fine.
Anyway this is the problem I see now and I really appreciate if somebody can give me solution or comment.
Then thanks for your taking your time to read this and I am looking forward to hearing from you soon.

Regards,

Sonny
sunlee.sti@gmail.com