Rockwell Automation 1756-RMxx ControlLogix Enhanced Redundancy System User Manual - Manual (Page 150)

150 Rockwell Automation Publication 1756-UM535D-EN-P - November 2012
Chapter 7 Program the Redundant Controller
Redundancy Object Attributes for Crossload Times
Before you complete calculations to estimate the crossload time, you need to use a
Get System Value (GSV) instruction to read certain attributes of the redundancy
object. These attributes are data transfer sizes measured in DINTs (4-byte words)
and are used to calculate the estimated crossload time.
This table indicates the two attributes you may choose to get specific to the
crossload data transfer size. Get the attribute value that meets your application
requirements.
Remember that the LastDataTransferSize attribute refers to the transfer size of
the previous crossload and synchronization point, which occurred prior to the
program containing the GSV instruction.
If you need to measure the crossloaded data from the last program in the task's
program list, you may need to add an additional program at the end of the task
that acquires the LastDataTransferSize value from the program that was formerly
at the end of the task.
TIP To get these attributes, you do not need to have the secondary chassis
installed or operating. If you do not have the secondary chassis operating,
the attribute values read indicate what data sizes would be transferred if
the secondary chassis was in use.
If you need the Then get this attribute value
Data size of the last data transferred during the last crossload LastDataTransferSize
Data size of the largest crossload of data MaxDataTransferSize