Modbus Slave -MBRead giving timeout error -4929
I am testing a Modbus Serial multidrop communication using 800XA 5.0 SP2 no revision, using CI853 .I have 7 devices in the modbus loop, when using Modbus simulator software and connecting the RS485 side using a converter i am able to communicate to all 7 devices with out any issue.
All devices are same model with same firware version and mapping adress also same ( Device is Sepam relay T82). Once our out controller card is connected, i am able to get the communication(data) to only 5 devices. Two devices are no givin the MBRear -4929 TIMEOUT message (no aswer from salve).
I tried lots of combination changed slave ID's, Change Card setting . Program done one for one device. Polling program speed changed. Card restarted, controller cold downloaded. Slave side cable removefd and connected.
I have similar two loops, second loop also two devices not communicating issue same as explaied above.
Is there any reason for this issue.
> "No error in hardware in ac800 side or slave side. All slaves are running with modus simulator software"
How do you KNOW there is no hardware error ?
- The modbus simulator testing proves your SOFTWARE configuration is OK - assuming of course that you tested running every node at the same time with multiple copies of a slave simulator. ie you simulated EXACTLY what you are trying to run in the field. Did you do this ?
- You haven't explained what you did to prove there is no hardware error....
-- Did you try a working PLC on a cable drop that wasn't working ? What happened ?
-- Did you try a "broken" PLC on a working cable drop ?
-- Did you try each PLC individually ?
-- Did you test every cable with a proven working modbus slave simulator ?