134 Rockwell Automation Publication 1756-RM100F-EN-P - October 2018
Chapter 6 Instruction Execution
Operand Changes
This section describes the changes to operands.
Converting +/- Infinity
Converting +/-Infinity to an integer results in MAX signed integer value with
MS flags set based on the value. For 32-bit integer machines, this means
2147483647 for +Inf and -2147483648 for -Inf. Overflow (V) is always set.
When writing/propagating +/- infinity values, 5580 and 5380 controllers offer
more standardized results.
MAX/MIN values are less common than 0 or -1 meaning there is less conflict
with common program results.
This implementation affects all instructions that store floating point values
into integer locations. Applicable to all languages.
Mitigation
N/A
IMPORTANT Manually determine the impact to your application and correct accordingly.
Language Affected
Ladder Logic (RLL) Yes
Struc tured Text (ST) Yes
Function Blocks (FBD) Yes
Sequential Function Chart (SFC) Yes
(1)
(1) Only affects the embedded Structured Text.
5580/5380 Controllers 5570/5370 Controllers
Writing infinity to an integer is the MAX signed value
that is permitted.
Writing +infinity to an integer is -1 value whereas -
infinity is stored as 0 in an integer.
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