M221 Modbus Serial to Multiple Slave

[Kanon.w]

Hi,

Trying to have M221 as master and multiple M200 as slave, I'm having trouble when there are multiple SL the communication is not working right, I'm guessing the master is read/write to multiple SL at once. When I set timer it starts to work decently but this doesn't seem viable for a lot of slaves since there will be a big delay the more SL there are. Is there a better solution for this?

I understand that IOscanner can do this easier but there is a limit to 16 devices. Attached simple program to read the heartbeat of SL

Thank you

[BennyN]

Only use 1 WRITE_READ_VAR at a time.

Use the Done bit to call the next modbus request.

With timers there is a risk of sending a new modbus request before receiving from previous request.

Yes, it is slow. Usually as a thumb rule, I count 100ms per device. Which means with 20 slaves it will take 2 seconds to get around. SE plc’s are a little bit faster, so maybe you can get it down to 50-80ms per device.