Rockwell Automation T80019 Application Note Working With Large Applications - Manual

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AN-T80019
Issue 1 Sep 08 AN-T80019 1
Application Note
Working with Large Applications
The 8110B processor has 1MB of memory set aside for storing the application, with another 1MB
allocated to allow an online update to be loaded without disturbing the running application. 64KB of the
1MB is allocated to storing the System.INI file, which is plenty because the System.INI files are rarely
larger than 15KB.
The remaining 960KB is allocated to the application download. A reasonable approximation to the size
of this download is the size of the appli.x6m file in the application folder after full compilation, although
this is not exactly the same data as the download. The download contains the application code, the
symbol table (database of variables) and if it is an intelligent update, a recipe of matches between the
old and new symbol table to allow the processor to copy the variable values for a bumpless transfer.
The intelligent online update recipe may be large or small, depending on the effect of the changes
made to the application. The symbol table contains all dictionary variables, but also internal variables
used to hold the value of corner connections, program constants and wires between function blocks in
FBD programs. The names of these internal variables are set at compilation and may change
depending on the effects of the editing on the source code. The update recipe must track all these
changes, and the recipe can be large or small depending on the hidden changes. This will change the
size of the download in an apparently random way.
For some large applications, the random size of the update recipe may make the download exceed
960KB, making the update impossible.
This document describes the factors that affect the size of the application download and advises on
how it can be reduced.
For technical support email: [email protected]
Issue Record
Issue
Number Date Revised by Technical
Check Authorised by Modification
1 Sep 08 Nick Owens Andy Holgate Pete Stock Initial Issue