Rockwell Automation 1785-CHBM ControlNet PLC-5 Hot Backup System User Manual - Manual (Page 104)

Publication 1785-UM024B-EN-P - January 2003
C-6 Data Table Crossloading
The On-Demand data table crossload operations that get performed
depend on the value written into the On-Demand Crossload
Command word. The 4 least significant bits of the On-Demand
Crossload Command word are defined for the 4 different On-Demand
data table crossload operations.
• Bit 0 - Timer Accumulators
• Bit 1 - Counter Accumulators
• Bit 2 - PD elements
• Bit 3 - User Selected Files
Thus, if you wrote a 15 (binary 1111) into the On-Demand Crossload
Command word, all On-Demand State crossload operations would be
performed. If you wrote a 5 (binary 0101) into the On-Demand
Crossload Command word, only the Timer Accumulators and the PD
elements would be crossloaded.
When the On-Demand State crossload is started, the On-Demand
Crossload Command word is cleared by the processor. While the
On-Demand State crossload is active, the processor ignores the
On-Demand Crossload Command word. This is true even if the
On-Demand State crossload was started from the other processor.
When an active On-Demand State crossload finishes, the processor
then checks to see if a new crossload command is in the On-Demand
Crossload Command word.
Qualification Crossloads
There are two separate crossloads that are automatically performed
during qualification. These qualification crossloads are only done if
the data table structures are identical between the two processors. The
first crossload performed during qualification is the Qualification data
table crossload. This crossload is performed when the processor is still
in Program mode. The second crossload done during qualification is
the Qualification State data table crossload. This crossload is
performed once the processor has transitioned into Run mode. Even
though the processor has transitioned into Run mode, qualification is
not complete until the Qualification State data table crossload is
complete.