Rockwell Automation 1785-CHBM ControlNet PLC-5 Hot Backup System User Manual - Manual (Page 108)

Publication 1785-UM024B-EN-P - January 2003
C-10 Data Table Crossloading
These error codes are identical to the Message Instruction Error
Codes. See the Instruction Set Reference Manual (Publication
6200-6.4.11) for a complete listing of the various error codes which
can be encountered while executing a Message Instruction.
For example, a qualification crossload could fail if the data table file
on the primary processor had read privileges disabled. This error
would show up as error code 0xF00B (privilege error) in word 53 of
the CHBI file.
Performing Data Table Crossloads Via Your Applications
On-Demand data table crossloading greatly simplifies the whole
crossloading procedure. However, you may have some special
crossloading needs that are not covered by On-Demand data table
crossloading. For example, if you want to crossload the data table data
over the Ethernet channel instead of the ControlNet channel, you
cannot use On-Demand data table crossloads. Or, perhaps you only
need to crossload certain elements within a file instead of the whole
file. Or, even if you need to crossload the entire Timer structure
instead of just the Accumulator subelement, On-Demand data table
crossloads do not meet those needs.
You can always perform your own data table crossloads using
message instructions. These message instruction crossloads can be
used in conjunction with On-Demand data table crossloads or they
can be performed separately. You are not limited to doing these data
table crossloads over the ControlNet channel.
We recommend that you have the message instruction rung qualified
with the backup state of the processor (e.g. secondary backup state).
Then the instruction will only be executed when the processor is a
secondary. A bit instruction can be used to condition the rung. Word 3
of the ControlNet Hot Backup Integer file contains the backup state of
the processor. Bit 2 is set if the processor is the primary. Bit 3 is set if
the processor is the secondary.
Since either PLC-5 can be the secondary processor, dual message
instructions are required. For example, if the node numbers are 1 and
2, there needs to be a message from node 1 to node 2 (if node 1 is the
secondary) and a message from node 2 to node 1 (if node 2 is the
secondary).