I have an assembly line that uses a 6ES5921-3WB14 (S5-130W System 3) CPU and I am looking at upgrading to a TIA Portal PLC.

I have converted most of the program but now have have come up against a problem.

The program uses SB's and I have never used these before.

From what I can gather from online research is that they are sequence blocks and I believe they are called from FB171, as the flag F240.7 used in the SB's is set in this FB. I don't seem to be able to find much information online as to how these SB's are called or programmed.

I cannot find any info at all relating to FB171 ABL:VERF, which I believe is a Siemens Library function, and I think that if I can understand how this function block works I might be able to understand the SB's and how they work, enabling me to re-program in a Graph function block in TIA Portal.

Does anyone have any info regarding FB171, the S5-130W manual or perhaps an old training manual for creating sequential blocks in Step5?

I have attached a document showing the FB171 call and the first couple of SB's in the program (there are around 200 SB's in total!!)