Allen-Bradley LOGIX 5000 Reference Manual page 310

Chapter 2 Drives
310
Description
The UPDN instruction follows these algorithms.
Condition Action
Hold is cleared AccumValue
n
and
Out = AccumValue
Initialize is
cleared
Hold is set and AccumValue
n
Initialize is
Out = AccumValue
cleared
Initialize is set AccumValue
n
Out = AccumValue
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
Structured Text
Condition/State
Prescan
Normal Execution
Postscan
Rockwell Automation Publication 1756-RM006K-EN-P - November 2018
= AccumValue + InPlus - InMinus
n-1
n
= AccumValue
n-1
n
= InitialValue
n
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.
Internal accumulator is set to zero.
N/A
EnableIn and EnableOut bits are cleared to false.
Action Taken
See Prescan in the Function Block table.
See Tag.EnableIn is true in the Function Block table.
See Postscan in the Function Block table.