FW 250 in S5?

Hi all

I'm busy converting an S5 program to S7.

I've come across FW 250 which I changed to MW 250 in my S7 program but something is niggling at me regarding Flag Words 250 and above... I'm not sure what it is?

Is it that these are retentive or something... somewhere in the darkest parts of my alcohol soaked skull I seem to recall that these flag words are special somehow..

Does anyone know whether this is the case or did I simply dream it?

In S5, FB200 to FB255 are the so-called 'scratchpad flags' and were often used for temporary storage inside reusable FB's.
Check within the particular program before using any flags in this range.

Thanks for the information

I'm not using any flags within the area, just converting to S7. I'm just going to convert FW 250 - MW 250, FW 252 - MW 252 etc

Can you see any potential problems with that?

(Its a 314C so MW 252 isn't out of its range)

Thanks for your help

The reason FW250 and above were used as scratch pad flags was because Siemens used these in their standard blocks as scratch flags.

If you are converting to S7, you would not need to do the same as S7 has built in scratch flags in the temp area.

It would be good practice to use the temp area instead, as these can be given a name appropriate to its use in the block, whereas using a scratch marker area, you could not give a meaningful name.

PeterW

Sorry for my ignorance but am I right in thinking that you are referring to the Variable Declaration Table.?

So, I would just declare some TEMPs in the VDT and use these in place of FW (MW) 200 and above...

Again, sorry if that's a daft question, thanks for your patience and clarification.

Cheers

Yes declare the temp/scratch bit/word, etc, in the temp declaration area at the top of the block.

Scratch flags are always contained in the block and must be conditioned before use and thrown away when the block is exited.

This is exactly what the temp flags are, with the added advantage that you can give them a meaningful name, so anyone can understand what they are.

Thanks for that Peter... will do that.

Thanks again for your help.

Cheers