Non-Transfer Area of State RAM
The designated registers in the Non-Transfer Area is ignored when state RAM values are transferred from the Primary CPU controller to the Standby CPU. Placing local date and I/O registers in the Non-Transfer Area can reduce the scan time.
NOTE: Due to the hardware design of the Quantum Hot Standby CPU processors, the scan time optimization provided by the Non-Transfer Area may be very low.
Using the Hot Standby tab of the editor dialog, designate a block of %MW words as a Non-Transfer area:
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STEP
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Action
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1
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Ensure that the Hot Standby tab is selected.
If you want to review the process for starting Control Expert and opening the editor dialog, please see Processor Configuration Screen. |
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2
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Enter the starting address in the system word %MW field.
The field is located in the Non-Transfer Area of the Hot Standby tab.
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3
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Enter the number of contiguous registers in the Length: field.
The field is located in the Non-Transfer Area of the Hot Standby tab.
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Transferring Standby CPU Data to the Primary CPU
The system words,%SW62/63/64/65 are dedicated to transfer data from the Standby CPU controller to the Primary CPU.
These system words can be used by the application program (in the first section of the MAST task) to register diagnostic information.
The data coming from the Standby CPU are transferred at each scan and are available to the Primary CPU.
When the secondary CPU is Offline, the reverse registers are not transferred to the Primary. If the user does not change the value on Primary side, this previous value is kept. When Secondary becomes the Standby, the reverse registers are updated on the Primary side 2 MAST cycles after the transition.
