Rockwell Automation T8451 Trusted TMR 24V dc Digital Output Module - 40 Channel - Manual (Page 11)

Trusted
TM
Module T8451
Issue 12 Apr 10 PD-T8451 11
1.5. Line monitoring and output states
The module automatically monitors the output channel current and voltage to determine the state of
the output channel. The numerical output state and line fault status are reported back to the
application and are represented below.
Description
Numerical
Output State Line Fault
Status
Field Short Circuit 5 1
Output Energized (On) 4 0
No Load, Field Open Circuit 3 1
Output De-energised (Off) 2 0
No Field Supply Voltage 1 1
Table 1 Line Monitoring Fault Status
It is recommended to fit a dummy load resistor to unused outputs to ensure a current is drawn that
exceeds the NO-LOAD threshold. This will prevent the module signalling a NO-LOAD fault.
1.6. Housekeeping
The output module automatically performs local measurements of several on-board signals that can be
used for detailed troubleshooting and verification of module operating characteristics. Measurements
are made within each slice’s HIU and FIU.
1.7. Fault Detection/Testing
Extensive diagnostics provide the automatic detection of module faults. The TMR architecture of the
output 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 output controls without interruption in the system or process. Faults are reported to
the user through the Healthy status indicators on the front panel of the module and through the
information reported to the TMR Processor. Under normal operations all three Healthy indicators are
green. When a fault occurs, one of the Healthy indicators will be flashing red. It is recommended that
this condition is investigated and if the cause 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.
From the IMB to the field connector, the I/O module contains extensive fault detection and integrity
testing. As an output device, most testing is performed in a non-interfering mode. Data input from the
IMB is stored in redundant error-correcting RAM on each slice portion of the HIU. Received data is
voted on by each slice. All data transmissions include a confirmation response from the receiver.
Periodically, the TMR Processor commands the onboard DSPs to perform a Safety Layer Test. The
SLT results in the DSP verifying with the TMR Processor its ability to process data with integrity. In
addition, the DSP uses Cyclical Redundancy Checks (CRC) to verify the variables and configuration
stored in Flash memory.
Between the HIU and FIU are a series of optically isolated links for data and power. The data link is
synchronized and monitored for variance. Both FIU and HIU have onboard temperature sensors to
characterize temperature-related problems. Each FIU is also fitted with a condensation sensor.