Rockwell Automation T8311 Trusted Expander Interface - Manual (Page 20)

Trusted
TM
Module T8311
Issue 12 Mar 07 PD-T8311 20
4. Operation
4.1. Operating Modes
4.1.1. Standby
Standby is the default mode of operation for the module, once internal supply levels are established. In
this mode the module may respond to command messages addressed to the module itself over the
IMB. Communication between the Controller Chassis IMB and the Expansion Chassis is inhibited.
4.1.2. Active
In the active mode, the module is responsible for the forwarding of messages from the Controller
Chassis IMB to the Expander Bus, and response messages from the Expander Bus to the Controller
Chassis IMB. The module also provides all of the functions available within the Standby mode of
operation.
4.1.3. Expander Interface Module Active/standby Control
The TMR Expander Interface Modules transition between active and standby (and vice-versa) is
controlled by command messages generated by the TMR Processor. Interlocks are incorporated
within the TMR Expander Interface Module to ensure that both modules within an active/standby
configuration can not assume active mode operation.
Where both modules within a pair are installed, the TMR Processor determines which module should
be active depending on its condition. Where both modules are healthy, the active operation defaults to
the left-most module.