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Rockwell Automation Publication 1756-RM100F-EN-P - October 2018 71
Replacement Considerations with CompactLogix and Compact GuardLogix Systems Chapter 3
The items that are highlighted in this table are where 5370 and older
controllers and the 5380 controllers behavior differ.
Because the 5370 and 5380 controllers have 32-bit data integrity, this only
applies to data structures larger than 32 bits. If word-level integrity is your
primary concern, the 32-bit data integrity does not impact your data use.
Good programming practice dictates the use of two unique words at the
beginning and the end of data. The controller validates the words to assure the
entire structure has data integrity. We recommend that the handshake data is
changed and the application code validates it every transaction before the
controller application code or higher-level system reading controller data acts
on it.
Table 13 - Behavior Differences
Tag Read/
Write Source
Tag Access
UID/UIE CPS Periodic Task
5380 Controllers 5370 Controllers 5380 Controllers 5370 Controllers 5380 Controllers 5370 Controllers
HMI Allows Blocks Blocks Blocks Allows Blocks
MSG Allows Blocks Blocks Blocks Allows Blocks
I/O Update Allows Allows Blocks Blocks Allows Allows
Produce/
Consume Allows Allows Blocks Blocks Allows Allows
Other User
Tasks Blocks Blocks Blocks Blocks Allows Allows
Motion
Planner Allows Allows Blocks Blocks Allows Allows
Blocks - Prevents source data values from change by communications during application execution.
Allows - Communications can change source data values during application execution.