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Product Overview
The Trusted® TMR Expander Processor Module resides in the processor slots of the Trusted Expander Chassis and provides the ‘slave’ interface between the Expander Bus and the Expander Chassis Backplane. The Expander Bus allows multiple chassis systems to be implemented using Unshielded Twisted Pair (UTP) cable connections whilst maintaining the fault tolerant, high bandwidth Inter-Module Bus (IMB) capabilities.

The Module provides fault containment for the Expander Bus, the Module itself and the Expander
Chassis, ensuring that the effects of these potential faults are localised and system availability maximised. The Module is fault tolerant with HIFT TMR architecture. Comprehensive diagnostics, monitoring and testing provide rapid fault identification. Hot-standby and module spare
configurations are supported, allowing automatic and manual repair strategies Features:

• Triple Modular Redundant (TMR), fault tolerant (3-2-0) operation.
• Hardware Implemented Fault Tolerant (HIFT) architecture.
• Dedicated hardware and software test regimes which provide very fast fault recognition and
response times.
• Automatic fault handling without nuisance alarming.
• Hot replacement.
• Front Panel indicators that show module health and status.

1.1. Overview
The TMR Expander Processor is a fault tolerant design based on TMR architecture arranged in a lock-step configuration. Figure 1 shows, in simplified terms, the basic structure of the TMR Expander Processor.
The Module has three main fault containment regions (FCR A, B and C). Each of the main FCRs contains interfaces to the Expander Bus and Inter-Module Bus (IMB), an active/standby interface to the other TMR Expander Processor in the Chassis, control logic, communications transceivers and power supplies.
Communication between the Module and the TMR Processor is via the TMR Expander Interface Module and the triplicated Expander Bus. The Expander Bus is triplicated, point-to-point architecture. Each channel of the Expander Bus comprises separate command and response media. Voting is provided at the Expander Bus Interface to ensure that cable faults are tolerated, and the remainder of the Expander Processor operates in a fully triplicated mode, even in case of cable faults occurring.
Communication between the Module and the I/O Modules in the Expander Chassis is via the IMB on the Backplane of the Expander Chassis. The IMB is identical to that within the Controller Chassis, providing the same fault tolerant, high bandwidth communications between the Interface Modules and the TMR Processor. As with the Expander Bus Interface all transactions are voted, localising faults to the IMB should they occur.
A fourth FCR (FCR D) provides the non-critical monitoring and display functions and is also part of the inter-FCR Byzantine voting structure.
Isolation is provided between FCRs wherever interfaces are required, to ensure that faults cannot propagate between them.

1.2. Power Distribution
The TMR Expander Processor Module derives its internal voltages from dual redundant +24 Vdc power supplied via the module connector from the Trusted Expander Chassis Backplane. Each FCR derives the required supplies independently.