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Old May 7th, 2009, 06:10 AM   #3
PeterW
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Canada

PeterW is offline
 
Join Date: Jun 2006
Location: Edmonton
Posts: 2,516
I usually keep MB0 for the cycle clock.

Usually the first scan bit is used to initialise parts of the program, in Siemens you would usually initialise these parts of the program within blocks called from the start up blocks, this saves having to use up scan time during the normal program sequence.

The only time I have seen a first scan flag used in a Siemens program was where this was used to set up pointers within instance DB's.

Apart from advanced programming such as that, any other thing (such as presetting states etc) can all be done within the OB100 calls.
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