Rockwell Automation T3441A ICS Regent DC Digital Output Module 24 VDC - Manual (Page 3)

(T3441A) DC Digital Output Module
P D - 6 0 1 5 M a r - 0 6
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When the output is logically turned on, the field device is
energized, and when the output is logically turned off, the
field device is de-energized.
Optical isolation between the module’s logic and field circuits
provides logic-to-field isolation — protecting the output
module from field signal over voltages, transients, and other
electrical disturbances. It also provides a safety barrier
between the primary field voltages and user accessible
circuits.
Each output is individually fused to protect the circuits from
short circuit conditions in output wiring and field devices.
Testing and Diagnostics
Each module’s voter circuits are periodically 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 voter is 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.
Fuses are continually checked for continuity. Field power
must be connected to the output module in order for it to
detect a blown fuse.
Front Panel Indicators
The 24 VDC digital output module is shown in Figure 2. The
front panel contains active and fault status indicators, a
shutdown indicator, blown fuse indicators (one per output
group) and an output status indicator for each output circuit.