I am getting a BF1 & SF on ET200 IM-153

Hello rk;

In any case where a diagnostic LED becomes active, information on the cause of the event is logged in the CPU's diagnostic buffer. I recommend that you open it and locate messages that refer to these faults and try to see what the CPU is complaining about.

If you have trouble deciphering the contents of the diagnostic buffer, use the Save As Text button (in the diagnostic buffer dialog) to upload the messages, then post the ones that correspond to your problem (probably linked to OB86, Rack Fault OB) here  in the forum so we can help you understand them.

Also, if your description is accurate and the I/O rack that exhibits the BF LED is the last one on the bus (physically the last one) you might face a termination problem. Check if the terminating resistor on the Profibus connector is active, in worst case change the connector for a new one and activate the resistor. If there is no termination on the bus then reflexions of the Profibus signals transit over the bus and destroy the data that is transferred, so it must be maintained properly at all times.

Hope this helps,

Daniel Chartier

Hello rk;

The way you describe the situation, it seems strange behaviour indeed.

In its present configuration, data is received redundantly by the masters without problem? The redundant ET 200M station shows no diagnostic LEDs, the diagnostic buffer shows no new messages on Loss of Redundancy for station 7?

Could you confirm that this station is actually the last (physically) on the bus, that the 2 Profibus cables arrive but do not leave the staton?

Could you post a picture (better) or a sketch of the ET 200M station, showing the On/Off status of the terminating resistors  and the Profibus cabling ?

Hope this helps,

Daniel Chartier