Rockwell Automation T8451 Trusted TMR 24V dc Digital Output Module - 40 Channel - Manual (Page 10)

Trusted
TM
Module T8451
Issue 12 Apr 10 PD-T8451 10
1.3. Host Interface Unit (HIU)
The HIU is the point of access to the Inter-Module Bus (IMB) for the module. It also provides power
distribution and local programmable processing power. The HIU is the only section of the I/O module
to directly connect to the IMB backplane. The HIU is common to most high integrity I/O types and has
type dependent and product range common functions. Each HIU contains three independent slices,
commonly referred to as A, B, and C.
All interconnections between the three slices incorporate isolation to prevent any fault interaction
between the slices. Each slice is considered a Fault Containment Region (FCR), as a fault on one
slice has no effect on the operation of the other slices.
The HIU provides the following services common to the modules in the family:
1.4. Front Panel Unit (FPU)
The Front Panel Unit (FPU) contains the necessary connectors, switches, logic, and LED indicators for
the front panel. For every module, the FPU contains the Slice Healthy, Active/Standby, the Educated
indicators (LEDs), and the module removal switches. Additional bi-colour LEDs provide status
indication for the individual I/O signals. Serial data interfaces connect the FPU to each of the HIU
slices to control the LED status indicators and monitor the module removal switches.
• High Speed Fault-Tolerant Communications with the TMR Processor via the IMB interface.
• FCR Interconnect Bus between slices to vote incoming IMB data and distribute outgoing I/O
module data to IMB.
• Optically isolated serial data interface to the FIU slices.
• Redundant power sharing of dual 24V dc chassis supply voltage and power regulation for logic
power to HIU circuitry.
• Magnetically Isolated power to the FIU slices.
• Serial data interface to the FPU for module status LEDs.
• SmartSlot link between active and standby modules for co-ordination during module
replacement.
• Digital Signal Processing to perform local data reduction and self-diagnostics.
• Local memory resources for storing module operation, configuration, and field I/O data.
• On-board housekeeping, which monitors reference voltages, current consumption and board
temperature.