116 Rockwell Automation Publication 1756-RM100F-EN-P - October 2018
Chapter 6 Instruction Execution
Structural Changes to
Execution
This section describes the structural changes to execution, and apply to the
following:
• JSR Nesting Level Limit
• Max Number of Inputs or Outputs for a Program JSR/RET
• Max Number of InOut Parameters for an Add-On Instruction
• Jump to Label Must Be Present
• MCR Placement
• Data Alignment and Memory Allocation Rules for User-defined Data
Types (UDTs) That Contain LINTs
JSR Nesting Level Limit
When you nest routines, the controller reserves enough memory to execute to a
maximum of 25 nesting levels. Previously, controllers let you continue to nest
until they ran out of stack space and faulted.
The major fault ‘Nesting limits exceeded’ signifies that you have exceeded the
nesting limit.
This implementation affects the JSR instruction.
Mitigation
Restructure your project to avoid excessive subroutine nesting. Resolve any
verification errors that occur when you open and import projects in the
Logix Designer application, version 28 or later.
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 embedded Structured Text.
5580/5380 Controllers 5570/5370 Controllers
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