Rockwell Automation T8311 Trusted Expander Interface - Manual (Page 9)

Trusted
TM
Module T8311
Issue 12 Mar 07 PD-T8311 9
1.1. Overview
The TMR Expander Interface 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
Interface.
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 Interface in the chassis, control logic, communications transceivers and power
supplies.
Communication between the module and the TMR Processor is via the IMB on the backplane of the
Controller Chassis. The IMB provides fault tolerance and high bandwidth communications between the
Interface Modules and the TMR Processor. All transactions are voted, localising faults to the IMB
should they occur.
Communication between the Interface Module and the TMR Expander Processor in the Expander
Chassis is via the 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.
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 can not
propagate between them.
1.2. Power Distribution
The TMR Expander Interface Module derives its internal voltages from dual redundant +24V dc power
supplied via the module connector from the Trusted
TM Controller Chassis backplane. Each FCR
derives the required supplies independently.