Reboot of CPU 315 - Siemens

Hi,


Can anyone explain the difference between rebooting a Siemens CPU 315-2 PN/DP, either by setting the switch into stop and back into run, versus turning the power off and back on?

I have a CP341 running as Modbus master towards external device. It has some issues, and freezes some times. Some times it does not help turning cpu switch to stop, and back to run, but it does help rebooting the 24VDC. This makes me wonder what the difference is, and if it has to do with buffers being cleared etc.


Thanks for any answers...

There is nothing functionally between removing power or using the STOP/RUN selector. In both cases, the CPU does a warm restart. I think your issue is with the CP 341.

sigmadelta said:

There is nothing functionally between removing power or using the STOP/RUN selector. In both cases, the CPU does a warm restart. I think your issue is with the CP 341.

Click to expand...

Can you explain to everyone the difference between cold start and warm start then? Can you also approach when OB102 and 100 are called as well?

Cold restart (OB102) is unavailable in the S7-300, only in the S7-400 and CPU 318-2DP (which is really a small-size S7-400 CPU).

Orense, check the diagnostics buffer of the CP341 (not the diagnostics buffer of the CPU).

When you say it freezes do you mean go into stop or just does not control i.e. program in PLC not functioning even though it is in run.

If run LED is on then I suggest this is a bug in the code and powering down resets some flags or if communication freezes then I think you need to look at PLC Code or Comms.