User Manual

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