Rockwell Automation T8424 Trusted TMR 120Vac Digital Input Module - Manual (Page 24)

Trusted TM Module T8424
Issue 8 Sep 11 PD-T8424 24
5. Fault Finding and Maintenance
5.1. Fault Reporting
Input module faults are reported to the user through visual indicators (LEDs) on the front panel of the
module. Faults are also reported via status variables which may be automatically monitored in the
application programs, and external system communications interfaces. There are generally two types
of faults that must be remedied by the user; external wiring and module faults. External wiring faults
require corrective action in the field to repair the fault condition. Module faults require replacement of
the input module.
5.2. Field Wiring Faults
The Trusted TM TMR 120VAC Digital Input does not support line monitoring for open or shorted field
loops. These faults will be reported to the TMR processor as a channel OFF state. Open circuit faults
between the T8824 and the module are detected and reported.
5.3. Module Faults
Extensive diagnostics provide the automatic detection of module faults. The TMR architecture of the
input module and the diagnostics performed ensure the validity of all critical circuits. Using the TMR
architecture provides a fault tolerant method to withstand the first fault occurrence on the module and
continue normal input measurements without interruption in the system or process. Faults are
reported to the user through the Healthy status LEDs on the front panel of the module and through the
INFO and HKEEPING variables. Under normal operations all three Healthy LEDs are green. When a
fault occurs, one of the Healthy LEDs will flash red. It is recommended that this condition is
investigated, and if the fault is within the module, it should be replaced.
Module replacement activities depend on the type of spare module configuration chosen when the
system was configured and installed. The module may be configured with a dedicated Companion
Slot or with a SmartSlot for a spare replacement module. Refer to Operator and Maintenance Manual
for module replacement procedure.
5.4. Companion Slot
For a Companion Slot configuration, two adjacent slots in a Trusted TM Chassis are configured for the
same input module function. One slot is the primary slot and the other a unique secondary (or spare)
slot. The two slots are joined at the rear of the Trusted
TM Chassis with a double-wide I/O Interface
Cable that connects both slots to common field wiring terminations. During normal operations, the
primary slot contains the active module as indicated by the Active indicator on the front panel of the
module. The secondary slot is available for a spare module that will normally be the standby module
as indicated by the Standby indicator on the front panel of the module.
Depending on the installation, a hot-spare module may already be installed, or a module blank will be
installed in the standby slot. If a hot-spare module is already installed, transfer to the standby module
occurs automatically if a module fault is detected in the active module. If a hot spare is not installed,
the system continues operating from the active module until a spare module is installed.