Thanks for the information.
I have 11 CP341's in the system, 2 are local and the remaining 9 are at various outstations (7 locations). I am using IM153-4PN modules to interface each outstation with my PLC (CPU 317-2 PN/DP)
If I am understanding you correctly, I should not be exceeding the number of active jobs I have available to me (8 reads and 8 writes) because I am accessing 9 out of the 11 CP341's via a state machine that calls only one instance of FB7 and FB8 (the state machine finishes each transaction off before progressing to the next slave device)
I have checked the documentation of the device (with which I need faster communications) and it states that the replied packed should always be sent within no later than 10ms after the device is polled.
I dont have an oscilloscope, but I can tell that the received packet arrives very shortly after the transmitted packet is sent as I see both the Tx and Rx LED's light up at the same time on the CP341.
Also, I have an application that is used to test the devices (the slave device in question) and there I can also see that the received packet arrives right after the transmitted packet was sent, there is no noticeable delay between Tx and Rx.
The only thing that I can think of right now is that currently I have the IO cycle Update time set to 512ms on each of the IM153-4PN modules. I had done this when I was debugging another problem I had during the early stages of this project.
I will change these settings back to default a little later, when it will be safe to stop the PLC, and I will let you know if this setting is causing the issue.
Thanks for the help.