GFK-0467K Chapter 2 System Operation 2-7
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time. In order to maintain accuracy, the actual start of sweep is recorded in 100 microsecond
increments. Each timer has a remainder field which contains the number of 100 microsecond
increments that have occurred since the last time the timer value was incremented.
Input Scan
Scanning of inputs occurs during the input scan portion of the sweep, just prior to the logic
solution. During this part of the sweep, all Model 30 input modules are scanned and their data
stored in %I (discrete inputs) or %AI (analog inputs) memory, as appropriate. Any global data
input received by a Genius C om m unications Module, an Enhanced Genius Communications
Module, or a Genius Bus Controller is stored in %G memory.
Modules are scanned in ascending reference address order, starting with the Genius
Communications Module, then discrete input modules, and finally analog input modules.
If the CPU is in STOP mode and the CPU is configured to not scan I/O in STOP mode, the
input scan is skipped.