Emerson ControlWave Instruction Manual page 65

Revised Nov-2010
ControlWave Instruction Manual (CI-ControlWave)
Handbook (D5125) for more information. That same manual includes
an I/O Mapping section that describes, for advanced users, the I/O map
for this module.
DO with Readback in a Redundant System
Variables in the ControlWave project govern how inconsistencies
between the online DO module and the standby DO module are
handled in redundant systems with DO readback. Information on
configuring system variables is included in the ControlWave Designer
Programmer's Handbook (D5125).
If there is a discrepancy between the value of the online and standby
DOs, the system sets a status variable to TRUE. For local I/O boards,
this is a system variable that follows the format:
_RDN_IO_n_ERR
where n is the I/O slot number of the DO module in the backup unit
that has a failure.
For boards residing in an I/O expansion rack, instead of a system
variable, a variable mapped by the _ER_STAT virtual status board
provides this indication. By default, the name of the variable follows
one of two possible formats.
ERSTAT_n_RDN_IO_x_ERR
ERST_n_RDN_IO_x_ERR
where n is the I/O slot number of the virtual ER_STAT board, and x is
the I/O slot number of the digital output module. See the I/O
Configurator and I/O Mapping sections of the ControlWave Designer
Programmer's Handbook (D5125) for more information. You can
optionally rename these variables.
You should configure these variables as alarms so you receive
notification of a failure of the backup DO module. See the
ControlWave Designer online help for information on alarm
configuration.
When a read-back failure occurs, the FAIL LED remains RED until the
unit reboots, 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 changes the LED back to
RED, and the associated _ERR error variable back to TRUE.
For boards installed locally in the controller (local I/O), another system
variable (_RDN_IOERR_WARN) determines whether a failure of the
standby DO (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
I/O Modules 3-17