Summary of programming considerations, Summary of programming considerations -22 – Rockwell Automation 1747-BSN Backup Scanner Module User Manual

Page 164

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Publication 1747-UM010B-EN-P - September 2003

9-22 Programming Techniques

Summary of Programming
Considerations

When developing a program for the SLC 500 backup system, you must
always consider the following:

•

non-synchronous I/O scans

•

execution times of block transfer instructions

•

time for transfer of data from the primary to the secondary
processor

•

the need to reduce the quantity of data to be transferred, and
gathering all related data into a single block

•

synchronization of discrete I/O data with regard to program
scans even though remote I/O scans are performed
asynchronously

•

the need to disable message instructions in the secondary
processor using the primary/secondary bit

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