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4-12-5 Reducing the Cycle Time
When a Special I/O Unit is mounted in a C200HX/HG/HE PC, END refreshing is
performed automatically each cycle without making any special settings. When
several Special I/O Units are being used, the cycle time might become too long
because of the time required for this automatic I/O refreshing.
To reduce the time devoted to I/O refreshing, disable cyclic Special I/O Unit
refreshing in the PC Setup (DM 6621) and use IORF(97) to refresh the Special
I/O Units instead. I/O refreshing for all Special I/O Units mounted to the CPU
Rack or Expansion I/O Racks can be disabled in the PC Setup by setting DM
6621 to #0100.
The following example program reduces the Special I/O Unit refreshing time for
a PC with four Special I/O Units by refreshing just one Unit each cycle. The Units
are refreshed in order: Unit 0, Unit 1, Unit 2, Unit 3, Unit 0, and so on.
Unit 0
Unit 1
Unit 2
Unit 3
C200HX/HG/HE
Special I/O Unit Interface Programs Section 4-12