Rockwell Automation T3488/T3488A ICS regent Monitored Guarded Output Modules - Manual (Page 4)

Monitored Guarded Output Modules (T3481/81A, 84, and 88/88A)
4 (Issue 2)
Industrial Control Services
when one output switch fails off (cases two and four in Table
1). The module failure is automatically detected and the
module can be removed and replaced without interrupting
output control.
Testing and Diagnostics
Automatic testing is performed on the monitored guarded
output modules as well as the field load connections.
Module Testing
Each voter and FPGA logic section of the Guarded output
modules are automatically tested by the processor modules.
Discrepant data are sent through one of three legs of the I/O
Safetybus to determine whether the module’s voters are able
to outvote the incorrect data. A failure to return the correct
majority-voted result to the processors produces an I/O
module error indication at the processor modules and a
module fault indication at the I/O module.
Each type of module has a unique identification code that is
read by the controller. This code lets the controller know
which type of module is installed in each I/O chassis slot and
how to address that module and its points specifically. If a
module is removed, or is replaced with a module of a different
type, the processor modules will indicate an I/O module error.
Loopback logic tests periodically write data to the module and
then read it back to determine whether the module’s I/O bus
interface logic is functioning correctly.
Output Circuit Testing
The output circuits of the monitored guarded output module
are automatically tested to detect failures in the redundant
output switch circuits on-board the module and also to detect
open and short circuits in the output field wiring and load
devices.
Output Switch Testing
To detect a failure in the redundant output switch circuits,
each output switch is checked for turn-on and turn-off
capability. Periodically, each output switch circuit on the
module is tested for its ability to change its current state.