MRX Instructions Fails Until Power Cycle

[belias]

I'm following up on an issue that I've been having for some time, where a particular MRX instruction will repeatedly fail - usually until a physical power cycle of the PLC.  This happens about once a month, and finally I was able to do some troubleshooting while it was occurring.

Code: [Select]

The basic outline of the program is:

---Stage 0---
Init variables
Goto Stage 1

---Stage 1---
MRX for Inverter 1
If successful, go to stage 2
If not successful, go to stage 9

---Stage 2---
MRX for Inverter 2
If successful, go to stage 3
If not successful, go to stage 9

---Stage 3---
1 second timer to go back to stage 0

---Stage 9---
Set error flag, 30 second timer to go back to stage 0

When the issue is happening, the program will pause on Stage 1, and then go to an error condition.

SysInfo shows ST143 is set with "Operation timed out...in SOLAREDGE_MODBUS @ 14" (see attached pic).  This line is the equivalent to Stage 1.

Some other info:

1.  This PLC also communicates with various other MODBUS units (similar MRX instructions) and these never have a problem

2.  When the issue is occurring, I can use a separate MODBUS program to read the parameters from Inverter 1 successfully

3.  I'm not sure if it's coincidental, but I noticed a "reboot following HW watchdog timeout" occurred before the communication errors started (see attached pic)

4.  In addition to power cycling the PLC, I found another way to correct the problem when it's happening: 

Modify the program so that Stage 0 goes to Stage 2 instead of Stage 1; write the program change; then change the program back so that Stage 0 goes to Stage 1 and write the program again.  Now it works fine.  It's almost like just "releasing" the device fixes the problem.


Any idea what might be going on?  Or how I can get some more troubleshooting info when it's happening?

Thanks.

[franji1]

1. Post a screen shot of your System Info page (General Information tab).

2. What device(s) are you using in your MRX instructions, Serial RTU or Ethernet TCP?  If Modbus/TCP, are you re-using the same Modbus/TCP Client device for all your slaves, or do you have a different Modbus/TCP Client device for each slave?

[belias]

1.  Sure - see attached pic

2.  All MRX instructions use Ethernet TCP and all MODBUS slave devices have their own BRX device


Thanks for the assistance.

[franji1]

Definitely update the firmware.  There have been some fixes to the Ethernet TCP stack to address issues similar to what you are seeing.

Run Live Update just in case, then install the latest firmware version for BRX  PLCs (2.10.3).
https://hosteng.com/HW-Products/DM1/BX-DM1_RevHistory.htm

That's good that all your Modbus/TCP devices are unique - this definitely helps with throughput since each can maintain their specific TCP connection.

Hopefully things will be good after the firmware update.