Allen-Bradley LOGIX 5000 Reference Manual page 33

Process Control Instructions
Description
The D3SD instruction controls a discrete device having three possible states, such
as fast/slow/off or forward/stop/reverse. Typical discrete devices of this nature
include feeder systems, and reversible motors.
Affects Math Status Flags
No
Major/Minor Faults
None specific to this instruction. See Common Attributes for operand-related
faults.
Execution
Function Block
Condition/State
Prescan
Tag.EnableIn is false
Tag.EnableIn is true
Instruction first run
Instruction first scan
Postscan
Rockwell Automation Publication 1756-RM006K-EN-P - November 2018
Action Taken
EnableIn and EnableOut bits are cleared to false.
EnableIn and EnableOut bits are cleared to false.
EnableIn and EnableOut bits are set to true.
The instruction executes
Set ProgOper to Operator Mode.
Set Command0Status to True.
Set Command1Status to False.
Set Command2Status to False.
The fault timer is cleared.
ModeAlarm is cleared to false.
All the operator request inputs are cleared to false.
If ProgValueReset is true, all the program request inputs are
cleared to false.
When OverrideOnInit is true, ProgOper is cleared to false(Operator
control).
If ProgHandReq is false and OverrideOnInit is true, Hand is cleared
to false and Override is set to true (Override mode).
If ProgHandReq is true, Hand is set to true and Override is cleared
to false(Hand mode).
EnableIn and EnableOut bits are cleared to false.
Chapter 1
33