GE Mark VIe System Manual page 110

4.4.1 Controller Redundancy to Prevent Loss of Communication
In a TMR controller set, each controller receives UDH EGD data independently from a direct Ethernet connection. If the
connection is broken, a controller can request the missing data from the second or third controller through the IONet. One
controller in a TMR configuration is automatically selected to transmit the EGD data onto the UDH. If the UDH fractures,
causing the controllers to be isolated from each other onto different physical network segments, multiple controllers are
enabled for transmission. These controllers provide data to each of the segments. These features adds a level of Ethernet fault
tolerance to the control system.
Note There are many features that make the Mark VIe control system fault tolerant, including the network configuration.
Unit Data Highway EGD TMR Configuration
Similarly, with dual redundant controllers, each controller receives UDH EGD data independently from a direct Ethernet
connection. If the connection is broken, a controller may request the missing data from the second through the IONet. One
controller in a dual controller set is automatically selected to transmit the EGD data onto the UDH. If the UDH fractures
causing the controllers to be isolated from each other onto different physical network segments, each controller is enabled for
transmission, providing data to both segments.
110 GEH-6721_Vol_I_BP GEH-6721_Vol_I Mark VIe and Mark VIeS Control Systems Volume I
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