Through various faults on the PROFIBUS (double-token etc.) it might happen that the CP 342-5 then withdraws from the bus. In doing so the CP 342-5 switches to the CLEAR operating mode. However, this event is not entered in the diagnostics buffer of the CPU. Nor is an alarm OB called in the CPU. The only way of finding out about this is via the communications blocks of the CP 342-5. For this you have 2 options:
- Evaluate the parameter DPSTATUS on FC 2 "DP_RECV".
Fig. 01: Sample call of DP_SEND
If Bit 5 is on FALSE and Bit 4 on TRUE in the DPSTATUS parameter, then the CP 342-5 is in Clear mode.
- Call FC 3 "DP_DIAG" with DTYPE 4 job
Fig. 02: Sample call of DP_DIAG
More information on evaluating the return parameters from the communications blocks is available in the Online Help of STEP 7. For this you select the required block in the block folder of your project (FC 1, FC 2 or FC 3) and press the F1 key.