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TDM Switch Function in the DAC

Once the gain is properly adjusted, the time-division multiplexed (TDM) switch function receives the incoming data and maps it to the appropriate destination. The TDM switch function samples the incoming multiplexed signal and sends the data over the TDM bus according to instructions provided by the microprocessor.

The TDM switch function reduces the constant delay to 125 ms for an 8-kHz signal. In addition, the variable frame width/bit level-switching feature allows for greater control between channels. The number of input streams, output streams, bits per time slot, and time slots per frame can be modified to meet specific system needs. Because many digital access cards (DACs) may introduce contention on the TDM bus, collision detection is enabled with a GTL+ bus I/O interface, available directly on the APEX II device. If a collision is detected, every card in the system can be notified via the Ethernet control bus.

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