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Using a Quantum IEC Hot Standby System
840 USE 106 00 January 2003 119
Hot Standby Command Register
Range You may enter any number in the range 1 ... n, where n is the last configured 4x
register. However:
the command register must be part of the area of state RAM that gets transferred
from the Primary to the Standby controller on every scan.
therefore the command register must not be within the range of the nontransfer
area, which you specify in the nontransfer area of the Hot Standby dialog.
Keyswitch
Override and
Run Mode
You may choose to override the keyswitch on the front panel of the CHS 110
modules for security or convenience. If you override the keyswitch, the command
register becomes the means for taking the CHS 110 modules on or offline.
By default, the keyswitch override is disabled. The Hot Standby dialog allows you to
enable it.
If you enable the keyswitch override, the Offline/Running operating mode of the
controllers at startup are determined by the values you set to bits 14 and 15 of the
command register. These bits are represented as the Run Mode for controller A and
B (depending on the designation slideswitch). Remember, that when the keyswitch
override is enabled you cannot initiate a program update (program xfer) at the CHS
110 module in the Standby rack.
As long as the keyswitch override is disabled the settings for the Run Mode may be
ignored.
CAUTION
Hot Standby Command Register Hazard
Be sure the register you select as the Hot Standby command register is
reserved for this purpose and not used for other purposes elsewhere in
user logic
Failure to follow this precaution can result in injury or equipment
damage.