Modicon M340 Readvar Communication Report 7

[Corsair]

I've got an M340 hitting an Ethernet to Serial converter one read at a time. Each read is enabled through a one-shot r_trig. I've got some extra time in between reads.

The CPU sometimes runs for awhile but eventually each read gets hung up with an error communication report 7. After that nothing gets the comms back except cycling power. I've tried the cancel bit, the cancel instruction, halting and back to run, shutting off the active bits before the read starts, etc.

Other posts on this forum seem to have found the same problem but I didn't see anything conclusive about a work-around. The CPU is in use in Alaska and they don't have a spare so updating the firmware concerns me. If I can tie it to a definite revision bug we can ship them a different CPU.

EcoStruxure V15

Thanks to all.

 

[Lare]

Sounds like data collisions on RS-side.


Have you used same gest parameters group for every read/write_var blocks?
As you can have only one modbus query active on RS232 or RS485 side, you don't need multiple gest parameters on M340 logic and sequencing and sending querys is easier to code.



This leads to that you need sequencer for communication. Add sequencer number every time with little delay when gest_parameter(1].0 is false.
(activity bit's false state enables ton timer delay for adding sequencer number)

Then you can communicate with this principle, only change you sequencer numbers to place of %S6 pulse before R_trig block.

http://www.plctalk.net/qanda/showthread.php?p=875957#post875957

 

[Saffa]

One of the registers in the GEST management array is a parameter is a timeout. If this is set to zero then the failed communication will not time out, and everything freezes. Put a value in here.. it is in multiples of 100ms, so a value of 10 will give you a 1 second timeout

I forget which word it is but it is shown in the help file.