Easy Modbus-Rtu Master - Slaves Freezing

[TxRx 0]

Hi everyone, I'm facing problems implementing the Easy modbus-rtu master solution kindly provided by PMCR. i'm working with a CJ2M, and i have a SCU41-v1 connected to 5 AC10 series Parker drives, using modbus at Port 1 (Protocol Macro as indicated in the manual- 2 wire). Everything works ok after powering up the system. Unfortunately, after a few minutes, one of the parker drives freezes communication. An hour later....another. And so on. If I reboot the drive, powering it off and on, it starts communicating again. Any ideas about what might be causing this? Thanx.

[lostcontrol 23]

Check the spec's on the parker drives. Some slave devices require regular writes so that they know that their 'master' is present.] Does the drive have anything indicating something like 'master comms fault'? The default setup of PMCR's Easy Modbus only writes on data change, for many reasons I guess. There are a few ways to make it write more reguarly, but no need to explore these until you know the cause of the slave freeze..

[TxRx 0]

Unfortunately the only parameters we get is to define drive's node, baud rate, parity, and rtu or ascii. I already changed the connection cable, decreased the baud rate, increased the number of retries, nothing seems to work. Right now i'm waiting for a reply from Parker. Thanks anyway for your sugestion.

[Michael Walsh 268]

As a test, you could have the code change the frequency reference by a tenth or hundredth of a Hz (if that does not cause problems) once every half an hour or so to see if this resolves the issue.