Hi,

I have a CPU 414-5 H PN/DP with fail-safe program. 

My problem is:

When i restart PLC from stop to run, the output of some of F_RS_FF blocks will be set, but i can not see any set bit in the SET input of them. This only occur on some of the pointed blocks. 

Guide me please 

Best regards

Tekabi

Hi Tekabi,

Which is the PCS7 & F-system version? 

Hi,

Thanks for your reply. 

Pcs7 version is 8.1, and f-system version is 6.1.

Regards 

Tekabi 

Hi Tekabi,

Is "S" input of F_RS_FF interconnected to any block IOs?

If yes, The trigger has come from and went out for a moment from the connected block. Since it is a RS_FF it has stored the value at output "Q".

Hi Taru,

The answer is yes. The S input is interconnected to block I/Os by or block with 3 inputs. 2 inputs of the 3 inputs caused to this problem. 

Regards

Tekabi