Hello,
from time to time one project experience communication problem. PLC program simply stop reading filed devices that are connected to it via CP440. It is a serial communication. It usually happens after there is a power outage on field devices.
Restart (Warm, Cold) of CPU doesn't solve the problem (Process can tolerate very short absence of control). Also switching off Power on PLC also doesn't solve the problem.
What solve the problem is performing clear CPU reset via PLC>Diagnostic....
However, right now this is not the option because plant is running and communication to the filed devices is not vital.
One simple example of communication is given here!
Real communication part is not very different. There must be some other way to "reset" this communication without disturbing PLC program. The communication is implemented with standard SEND_440 and RECV_440 FB10 and FB9 blocks.
Did anyone have similar problem?
Thank you in advance!
from time to time one project experience communication problem. PLC program simply stop reading filed devices that are connected to it via CP440. It is a serial communication. It usually happens after there is a power outage on field devices.
Restart (Warm, Cold) of CPU doesn't solve the problem (Process can tolerate very short absence of control). Also switching off Power on PLC also doesn't solve the problem.
What solve the problem is performing clear CPU reset via PLC>Diagnostic....
However, right now this is not the option because plant is running and communication to the filed devices is not vital.
One simple example of communication is given here!
Real communication part is not very different. There must be some other way to "reset" this communication without disturbing PLC program. The communication is implemented with standard SEND_440 and RECV_440 FB10 and FB9 blocks.
Did anyone have similar problem?
Thank you in advance!
