Emerson ControlWave Instruction Manual page 77

Revised Aug-2015
ControlWave I/O Expansion Rack Instruction Manual
unit is rebooted, either through a sideload, forced redundant
switchover, or power-down and restart, or you remove and replace the
board (hot card replacement). Each of these operations momentarily
turns the FAIL LED to GREEN (and the associated _ERR error
variable to FALSE) until a new readback failure occurs, which will
change the LED back to RED, and the associated _ERR error variable
back to TRUE.
Another variable you must have mapped from the _ER_STAT virtual
status board named either ERSTAT_RDN_IOERR_WARN (or
ERST_RDN_IOERR_WARN) determines whether a failure of the
standby AO (as indicated by the LED and associated _ERR error
variable) should only be treated as a warning condition, which would
still allow a failover to occur, or as an error which would prevent a
failover to the standby. Note: Those are the default names; you can
change them as needed.
When you set this variable to FALSE, an AO readback failure in the
associated device is treated as an error; failover is inhibited. When you
set this variable to TRUE, an AO readback failure in the associated
device is treated as a warning that does not prevent a failover, and the
only reporting is via the _ERR variables and LEDs discussed, above.
Note: In the I/O Configurator, you must associate these boards with a
cyclic task, and the task must not run faster than 10
milliseconds.
I/O Modules 3-29