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Product Advisories: C ompactLogix, ControlLogix, DriveLogix, FlexLogix, and SoftLogix Controllers Using the Sequential Function Chart Editor

Ref: ACIG 2005-06-002  Date: June, 2005

Product Identification

Product Service Advisory is to inform you of a functional issue that exists with:

This Advisory explains the functional issue and the steps being taken to rectify the situation. Due to the nature of the problem, this effort has been assigned a Type II Mandatory Product Service Advisory– participation by applicable Company Field personnel is mandatory.

Problem Description

With the CompactLogix, ControlLogix, FlexLogix, and SoftLogix controllers listed above, hereafter referred to as the controller, the following functional issue exists:

If you have an SFC with nested simultaneous branches, it is possible for the controller to begin executing at an unexpected step. Following the convergence of a nested simultaneous branch, if the SFC loops back to the initial step of the parent branch, instead of executing that step, the SFC can jump to a step of another path in the nested simultaneous branch. For example:

Execution starts at Step_000. When Tran_000 becomes true, Step_001, Step_002 and Step_003 should become active. However, because the nested simultaneous branch in the left path converges and loops back to its parent step (Step_001), the active steps will actually be Step_005, Step_002 and Step_003.

Temporary Workarounds

To avoid this functional issue, never loop back to the initial step of a simultaneous branch after converging a nested simultaneous branch.

For example, in the SFC above, add a Step and Transition pair (Step_001A and Tran_001A) before Step_001. Make the condition for Tran_001A always true so that it executes in one scan. This makes the target of the loop back a step other than the parent step of the nested simultaneous branch. However, this also makes the SFC execution take one extra scan to get to the nested simultaneous branch when Tran_000 first becomes true.

Problem Correction

The functional issue described above will be corrected in the following revisions of these controllers :

Note that RSLogix 5000 version 15 no longer supports these controllers:

This anomaly will also be corrected in a future version of revision 13, estimated to be available in the August, 2005 timeframe, for the following controllers: