Rockwell Automation Publication 1756-RM100F-EN-P - October 2018 131
Instruction Execution Chapter 6
Subroutines Do Not Affect Math Status Flags
Subroutines are not considered MSF producers, so they do not preserve math
status flags across calls. The JSR, SBR, RET, FOR, BRK instructions are not
math status flags producers. FOR and BRK instructions do not affect math
status flags because they do not pass any parameters.
The JSR instruction saves (and reinitializes) the flags on entry and restores
them after the subroutine returns. Also, the SBR, RET, FOR, and BRK
instructions do not change the flags.
This implementation affects the JSR and FOR instructions. FOR is only
available in RLL.
Mitigation
N/A
Language Affected
Ladder Logic (RLL) Yes
Structured Text (ST) No
Function Blocks (FBD) No
Sequential Function Chart (SFC) Yes
(1)
(1) Only affects embedded Structured Text.
5580/5380 Controllers 5570/5370 Controllers
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