Allen-Bradley ControlNet PLC-5 User Manual page 63

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.
Qualification Data Table Crossload
The Qualification data table crossload occurs when a processor in the
No Control state transitions from Program mode to Run mode, and
the other processor is the primary processor. This complete data table
crossload is performed while the qualifying PLC-5 system is still in
Program mode. It is necessary to remain in Program mode until the
complete data table crossload is finished in order to prevent the
qualifying system from major faulting or going off into an odd state
due to uninitialized data table values.
Data Table Crossloading
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