adccommunitymod (AutomationDirect) asked a question.
Productivity Series Modbus RTU RS232 Port Reset
Created Date: October 15,2019
Created By: jfrye
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Is it possible to clear the buffer for a RS232 port using Modbus RTU protocol, or reset the port without power/stop cycling the PLC? Need to be able to do this remotely once a fault condition occurs on the port. We have several remote sites using P1Ks being polled by a P2K master over VHF radio, and the P1K ports appear to be locking up/timing out/ whatever you want to call it but they stop transmitting data, however the local processes are still fully functional.
Created Date: October 15,2019
Created by: jfrye
Is it possible to clear the buffer for a RS232 port using Modbus RTU protocol, or reset the port without power/stop cycling the PLC? Need to be able to do this remotely once a fault condition occurs on the port. We have several remote sites using P1Ks being polled by a P2K master over VHF radio, and the P1K ports appear to be locking up/timing out/ whatever you want to call it but they stop transmitting data, however the local processes are still fully functional.
Created Date: October 17,2019
Created by: NevergoldMel
Run the power for the radio or the serial RX line through an output relay and have that toggle off for 5 seconds when you can detect a loss of communication (stale heartbeat or some such).
Created Date: October 17,2019
Created by: jfrye
To follow up, we setup our screen to monitor the RS232 status bits, heartbeat, timeout, port ready, and everything is normal (first 2 off, and port is ready). There are no Tx signals out of the RS232 port on the CPU, but there are Rx signals; switch the CPU from Run to Stop and back again and the port starts transmitting and receiving. Everything appears to be fine with the radio, and between the radio and the CPU, just from the CPU to its own RS232 port...
Created Date: October 20,2019
Created by: NevergoldMel
Is line 6 tied to ground?
Created Date: October 21,2019
Created by: jfrye
Line 6 is not, Line 1 is.
Created Date: October 22,2019
Created by: NevergoldMel
Line 1 and 6 are both shown as 0v try tying them both to ground.
Created Date: October 22,2019
Created by: kewakl
Maybe, if you can, post the p1k comms logic.
Could be an interlock issue. ?
Created Date: October 24,2019
Created by: jfrye
There are no comms on the P1Ks, they are being polled by the P2K. Below is one rung for one P1K from the P2K. We have checked the obvious, rs232 cable wiring both ends, settings, etc. We can try tying pin 1 and 6 to gnd(0V).
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Created Date: October 24,2019
Created by: ADC_CommTeam02
If communicating from a P2K to a P1K there is no need to use Modbus. You can use RX/WX instructions to poll the data from the P1K. I would try a simple one rung program in the P2K to test communications then go from there.
Created Date: October 28,2019
Created by: OpZed
So it's serial ModbusRTU over VHF Radio? How many slaves? Can you post your CPU serial port setup? Have you tried adding a higher "Modbus Character Timeout " ?