Rockwell Automation T8424 Trusted TMR 120Vac Digital Input Module - Manual (Page 26)

Trusted TM Module T8424
Issue 8 Sep 11 PD-T8424 26
5.7. Transfer between Active and Standby Modules
The TMR Processor is responsible for managing a pair of I/O modules through an active/standby
changeover. The following rules apply to active/standby changeovers, though the TMR Processor and
not the I/O module enforce them:
Under normal conditions, an active/standby changeover will only occur if the new active module is
fault-free. Under some circumstances, it is desirable to be able to force a changeover to a known
faulted module. This can be accomplished by opening the Module Removal switches on the currently
active module and pressing the push-button reset on the TMR Processor. This will force the
changeover to proceed even if the new active module is not fault free.
• The user must define the primary, and optionally the secondary, I/O module location for each
I/O module pair. Each primary module location must be unique and is defined as part of the
complex equipment definition within the IEC1131 TOOLSET. Secondary module locations
can be unique or shared between multiple secondary modules and are defined within the
module’s section within the System.INI file. The system will automatically determine the
secondary module position if the primary module is installed and is operable.
• On initial start-up, if the primary module is installed, it will become the active module by
default. If the secondary module has been defined within the System.INI file and no primary
module is present, and if the secondary module location is unique, the secondary module will
become the active module by default. If the secondary module is installed with no primary
module present, and the secondary module location is not unique (as in a SmartSlot
configuration), then NO module for that module pair will become active.
• In order for a module to become the active module, the TMR Processor will verify that the
module is the correct I/O module type and that both Module Removal levers (and hence micro
switches) are closed. At this point the I/O module is configured and eventually placed in the
active state.
• A module in the active state should never be removed.
• When a fault occurs on the active module, the TMR Processor will be informed. Once it
becomes aware of the fault, the TMR Processor will attempt an active/standby changeover.
• An active/standby changeover starts with the TMR Processor checking to see if a standby I/O
module is installed. If no standby I/O module is available, the TMR Processor will continue to
utilise the active module and will continue to check for an available standby I/O module. Once
a standby module is found, the TMR Processor will verify that the I/O module is of the correct
type, that both Module Removal switches are closed, and that the I/O module is a part of the
correct module pair by using the SmartSlot link. At this point, the TMR Processor will
configure the standby I/O module with the same configuration information as the currently
active I/O module and place the standby I/O module into the standby state. The active
module is then placed in the maintain state (which suspends field loop testing), and any
module specific changeover data is transferred. The educated light flashes amber before the
active/standby changeover takes place, to indicate transfer of dynamic change over data
(COD). The previous standby module then becomes the active module and the original
module becomes standby. If the currently active module does not successfully complete the
self-tests, the TMR Processor will revert it to the standby state, and the module in the
maintain state will revert back to the active state.
• When both Module Removal switches are opened on an active module, regardless of the
module fault status, the TMR Processor will treat it as a request to perform an active/standby
changeover.