Ericsson LBI-39224 manual Redundant Clock Configuration, 200

LBI-39224

the Backplane. The MOM Controller Board controls clock selection by sending clock select command signals to all other Controller Boards within the CEC/IMC. Each Controller Board then controls the clock select circuitry on its respective Audio Boards.

NOTE

The redundant clock feature should only be enabled if the CEC/IMC is equipped with Audio Boards 19D903302P1 Rev. K (and later) and/or 19D903302P3. DO NOT enable the redundant clock feature if the CEC/IMC uses 19D903302P1 Rev. J or earlier Audio Boards.

If any of the selected clock pulses fail ("A" or "B" clock), clock monitoring circuitry on the Audio Boards signals their respective Controller Board. The informed Controller Boards then signal the MOM Controller Board, and if the redundant clock feature is enabled, the MOM Controller Board then commands all other Controller Boards in the CEC/IMC to switch their Audio Boards to the other clock circuit.

Redundant Clock Configuration

The initial start-up or default clock circuit is "B." If the MOM and two other Controller Boards report a "B" clock circuit problem, the MOM will switch clock operation to the "A" clock. Similarly, the MOM will also switch back to the "B" clock if a problem exists with the "A" clock. This redundant clock circuit selection can be enabled and disabled at the CEC/IMC Manager.

NOTE

If two or more Clock Boards are installed, corresponding clocks on the different Clock Boards should never be turned on ("A" and "A" for example). If only a single Clock Board is installed, both clocks should be turned on when the redundant clock feature is enabled ("A" and "B").

Panel-mounted toggle switches on the Clock Boards allow independent enable/disable control of the FUTUREBUS transceivers so multiple

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