Rockwell Automation T80018 Application Note Function Block Diagram Program Check - Manual

Trusted TM
AN-T80018
Issue 2 Jul 08 AN-T80018 1
Application Note
Function Block Diagram Program Check
Technical Alert TA20005 describes two issues where a function block diagram (FBD/LD) program may
not function correctly.
(1) Compiler Limit Issue
There is a limit to the total number of unique nodes in an FBD/LD program. Nodes include variables
and function/function block icons. Once that limit has been exceeded, the compiler will fail to produce
any application code for that particular program, without producing any errors or warning. The
downloaded application will contain no code for that program and none of its logic will work. This only
applies to large FBD/LD programs.
(2) Function Block Editor Limit Issue
Each node is assigned an ID number. There is a maximum ID number that the editor can assign. Once
past this limit, the editor will “wrap-around”. After this occurs, there is a possibility that the editor will
inadvertently assign a duplicate node number. Once a duplicate ID has been assigned, the compiler
will produce incorrect code, as only the node referenced by the initial duplicate ID is used. Some of the
logic in the program will operate incorrectly. This only applies to very large FBD programs or for FBD
programs that have undergone extensive and repeated changes.
This document describes how to check for the two issues using a utility program available from
[email protected].
Issue Record
Issue
Number Date Revised by Technical
Check Authorised by Modification
1 Jul 08 Nick Owens Pete Stock Gerry Creech Initial Issue
2 Jul 08 Nick Owens Pete Stock Gerry Creech Encrypted applications