Theory of

DC-1 Theory of Operation is divided into three sections: digital, analog and Operation video. The digital section discusses the Z80 host processor and its peripherals, system clocks, the PIC microcontroller, the Lexichip and 56004 digital signal processors, and the upgrade path for discrete 5.1 sound capability. The analog section includes the signal paths for both analog and digital audio inputs, A/D

and D/A conversion, level controls and the power supply. The video signal paths and on-screen display are discussed in the third section.

The digital section of the DC-1 is capable of receiving two channels of 20-bit audio. This is first processed by the Lexichip digital signal processor. In surround modes, the stereo pair is decoded and used to create up to seven channels. Other effects include reverb and ambience programs. The seven channels of audio are then passed serially to a 56004 processor which adds equalization and creates the subwoofer output. The 56004 outputs are then sent to the D/A converters for output conversion.

Digital Theory

An upgrade path is provided for discrete 5.1 surround. For the Dolby Digital upgrade, AC-3 encoded data is passed to a Zoran 38500 DSP processor which unpacks and decodes the surround data. Its six outputs are transmitted to the Lexichip as serial data multiplexed onto a single line clocked by a 256fs bit clock.

The Z80 host processor is responsible for all host control functions as well as slave DSP duties. Host functions include front panel display and switches, receiving IR input, On Screen Display, input and output level control, and Lexichip and 56004 initialization and parameter update. Refer to the following block diagram and the Main Board scematic sheets 1 -10 for the digital section.

Digital Block Diagram

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