12ć2 – Rockwell Automation 1775-S4B,D17756.5.3 User Manual SCANNER/MSG HND User Manual

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Execution Time Considerations

Chapter 12

12Ć2

You also might consider purchasing a Peripheral Communication Module
(cat. no. 1775-GA). This module features a faster executing enhanced
version of report generation. Contact your Allen-Bradley representative for
more information on this product.

Procedure execution times are slower if you use complex formats for
addresses. For example, the 1775-S4B scanner takes longer to find the
word at extended address E3.1.8.5.0.2 than at data table address B5:2 even
though these addresses reference the same word in memory. If you use a
symbol to define part of an address, the 1775-S4B scanner takes more time
to find the word. The 1775-S4B scanner can find a symbolic address in
less time than a complex extended address, but in more time than a simple
logical address.

The 1775-S4B scanner lists procedural user symbols, interprocedural user
symbols, local system symbols, and global system symbols in their own
symbol table.The 1775-S4B scanner fills each table with the corresponding
symbols in the order that you create them. The 1775-S4B scanner can find
a symbol at the beginning of the table in less time than one at the end of
the table. Therefore, to save time, you should define the most used symbols
first so that they are at the beginning of their corresponding symbol table.
Renaming a symbol does not change its placement in the corresponding
symbol table.

In a procedure, you can assign a value to a user symbol for later use in the
procedure. You can also assign a value to a data table address for later use
in the procedure. The 1775-S4B scanner takes more time to assign values
to user symbols than to data table addresses.

As we described in chapter 5, you can enter a semicolon (;) followed by a
comment to document each line of your procedure. If you enter comments
in your procedure, it takes the 1775-S4B scanner longer to execute the
procedure. If execution speed is critical in your application, you should
consider: