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Appendix C

Configuring the Sec8k Clock

This appendix describes how to configure the secondary 8 kHz clock to serve as a backup MVIP clock signal.

If the clock master board's T1 or E1 connection fails, the board immediately starts using its on-board oscillator to drive the MVIP clock. Since the oscillator cannot use the T1 or E1 clock as a reference when the connection is broken, it eventually loses synchronization with the trunk clock. Therefore, another clock source synchronized with the T1 or E1 line must be found as soon as possible to avoid framing problems.
If another board on the MVIP bus is an AG-T1 or AG-E1 also connected to a trunk, you can cause it to drive a secondary "backup" clock line on the bus, synchronized with the trunk's clock. This clock is called the secondary 8 kHz bus clock (Sec8k clock). The clock master can synchronize with the Sec8k clock temporarily if its trunk connection fails. (See Figure 34.) Figure 34. MVIP Bus Using Sec8k Clock

To configure the Sec8k clock: Edit your AG configuration file. Find the Board x section for the AG-T1 or AG-E1 board that will drive the Sec8k clock. In this section, set DriveSec8k to NET1. In all other Board x sections, set DriveSec8k to NO. Close the file, saving your changes. Run agmon again to make your changes effective. Note: agmon only configures Sec8k, and will not automatically switch clock references if there is a clock failure. The application must poll the board for error conditions, and switch clock references when necessary. To learn how to do this, see your CT Access documentation.
The Sec8k clock is also used to synchronize MC1 communications. For more information, see your MC1 documentation.

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