So I have this 2-wire P2000. The total bus cable length is about 200 feet.
There are 10 stations, each station with 2 PID controllers. Each PID controller has a power switch, and each power switch also turns on an input on the PLC that determines if a task runs (IE the tank's task does not run if the PID controller isn't on).
Each task has 4 modbus read instructions, giving 36 modbus reads all together. I'm getting crazy timeouts. This seems to me to be because I am sending 36 instructions into the read queue at the same time. I've called AD tech support, and it was suggested I use automatic polling, but this yields similar results, as even if you have a 500 MS polling rate, and offset the reads by 25ms or 50ms, you still get a "wraparound" effect where the queue gets loaded back up.
I can't exactly increase the network speed, because another device on the network is limited to 9600bps N 8 1 and the configuration can not be changed (lucky me).
I was looking for some ideas on how I can control this efficiently to stop all of these timeouts, or if someone happens to have the information, the size of the queue for modbus serial in a P2000 CPU.
Thanks.
There are 10 stations, each station with 2 PID controllers. Each PID controller has a power switch, and each power switch also turns on an input on the PLC that determines if a task runs (IE the tank's task does not run if the PID controller isn't on).
Each task has 4 modbus read instructions, giving 36 modbus reads all together. I'm getting crazy timeouts. This seems to me to be because I am sending 36 instructions into the read queue at the same time. I've called AD tech support, and it was suggested I use automatic polling, but this yields similar results, as even if you have a 500 MS polling rate, and offset the reads by 25ms or 50ms, you still get a "wraparound" effect where the queue gets loaded back up.
I can't exactly increase the network speed, because another device on the network is limited to 9600bps N 8 1 and the configuration can not be changed (lucky me).
I was looking for some ideas on how I can control this efficiently to stop all of these timeouts, or if someone happens to have the information, the size of the queue for modbus serial in a P2000 CPU.
Thanks.