B
Update local, expansion.
D
Scan Local and expansion inputs
Execute Global Tasks
Feed the CPU
Start counting ladder scan time
Execute main Ladder
Stop counting ladder scan time
Execute First Scan operations (1. Initialize special inputs and outputs. 2. Load Digital filter constant.)
C 
Update High speed
counter registers
Update local,
expansion and PWM
outputs
Feed
Respond to the
monitor query (if any)
on USB.
Stop counting main loop
scan time
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