Minor Fault On Overflow - Allen-Bradley ControlLogix 5570 Reference Manual

Chapter 6 Instruction Execution
Language Affected
Ladder Logic (RLL) Yes
Structured Text (ST) Yes
Function Blocks (FBD) Yes
Sequential Function Chart (SFC) Yes
(1) Only affects embedded Structured Text.
128

Minor Fault on Overflow

You can now generate overflow minor faults. Report Overflow Faults is a new
parameter that lets you enable Minor Overflow fault reporting.
Report Overflow Faults appears on the Controller Properties Advanced Tab:
• If you convert a legacy project to a 5580 or 5380 project, this parameter
defaults to enabled to keep legacy behavior.
(1)
• If you create a 5580 or 5380 controller project, this parameter defaults
to disabled to improve performance.
• In either case, you can override the default by changing the checkbox in
the Controller Properties Advanced tab.
Not monitoring overflow events in the minor fault log can reduce controller
overhead.
This implementation affects all instructions that can overflow.
By default, these controller do NOT trigger a minor fault.
• If you expect a minor fault condition that you must
monitor, use the S:V math status flag following
candidate instructions.
• If you want to monitor all overflow minor faults, then
enable the Report Overflow Faults property on the
controller Advanced tab.
Mitigation
If you want to monitor overflow conditions for specific instructions capable of
generating a minor overflow fault, insert XIC(S:V) immediately following
each instruction.
If you want to monitor all possible minor overflow conditions, set Report
Overflow Faults on the Controller Properties Advanced Tab and check the
minor fault log for their occurrence.
Rockwell Automation Publication 1756-RM100F-EN-P - October 2018
5580/5380 Controllers
ATTENTION: Enabling Report Overflow Faults can slow down your program
scan times.
5570/5370 Controllers
In these controllers, the controller always triggers a
minor fault condition when a math overflow occurred.