Step 7 Temp Local variable.

shaun_nel

Member
Join Date
Sep 2009
Location
Ladysmith
Posts
10
Hello All,

I am not new to Step 7 programming but I am also by no means totally conversant in all the methods available to "create" the desired software for the clients purpose.
I have recently moved across to a new plant where the suppliers have used FBD as the default programming language and there is a liberal use of local TEMP variables between networks. (See #Tmp_Bool in attached screen capture.)

I don't understand what the purpose of the re-use of the #Tmp_Bool variable is in this situation? Why not just use a different variable each time, so that the normal plant tech like myself can see where the data is going?

How would a person follow the logic if each network output end in #tmp_bool?

Any help will be greatly appreciated.

Thanks,
Shaun Nel.

Temp_Bool.jpg
 
He's using a temp bool to complete a network that needs a coil but his logic has no need of a coil. His network is all about the 2 move instructions, he wanted them to be on the same network but 2 moves in parallel need a coil at the end to complete the network.

I usually call the bool a 'dummy' when doing this.

Another reason people use a scratch, is if the network is too long to reasonably monitor, so they split it into 2 or 3 networks, using a temp bool to pass the status from one to the next.
 

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