Simatic S5

G,Day Guys,
With reference to the Siemens S5 package, I've just come across the expression "Scratchpad" Flags, F200.0-F255.7.

Whilst I,m aware of the term Scratchpad, and it's use but I'm not sure, how it works.

I've come across the term "Temporary" Flagword in several programs, where the same bit is used over and over again, in the program, but am unsure how this works.

Can someone please explain.

Regards

Norm.

Norm

Temporary flags are used within our programs, the reason why we use them is because there are not enough F's to go round. We have set aside 8 bytes of flags for temporary use.

The term 'double coil syndrome' comes to mind when dealing with temporary flags, if you are not familiar with that term, search this forum for an explanation of double coil syndrome.

As the program scans it will 'set' the flags as governed by the controlling logic, for example in PB1, network 1, the controlling logic sets flag F0.0 (TMPF0_0), we can now use this flag in it's 'on' state as we would with any flag that is used only once in the program, TMPF0_0 will stay in this 'on' state until it's state is 'written' over by other logic in the program.

So, in network 1 the 'coil' is address as a temporary flag, TMPF0_0. In network 15, the coil is again address as TMPF0_0, so the networks in between (network 2 to 14) where a contact bit of TMPF0_0 is used, will use the state set in network 1, any contacts of TMPF0_0 in the program after network 15 will use the state of this flag set in network 15, and so on.

Paul

The "scratchpad" flags are used by the standard function blocks. The documentation for the blocks usually specifies the amount of scratchpad flags used. If you're using the scratchpad flags in your program, there's no guarantee they'll have the same state after processing of a standard FB.