HP DC71XX, DX61XX 5.8.3 Audio Codec

Input/Output Interfaces

5.8.3 Audio Codec

The audio codec provides pulse code modulation (PCM) coding and decoding of audio information as well as the selection and/or mixing of analog channels. As shown in Figure 5-13, analog audio from a microphone, tape, or CD can be selected and, if to be recorded (saved) onto a disk drive, routed through an analog-to-digital converter (ADC). The resulting left and right PCM record data are muxed into a time-division-multiplexed (TDM) data stream (SD IN signal) that is routed to the audio controller. Playback (PB) audio takes the reverse path from the audio controller to the audio codec as SD OUT data and is decoded and either routed through an equalizer or applied directly to the digital-to-analog converter (DAC). The codec supports simultaneous record and playback of stereo (left and right) audio. The Sample Rate Generator may be set for sampling frequencies up to 48 KHz.

The integrated analog mixer provides the computer control-console functionality handling multiple audio inputs.

						Audio
						Format
	Mic In		S	Left		Rec
			e
	LineIn(L)		l	Audio	Rec	Data(L)
						ADC
	LineIn(R)		e		Gain
						Rec
			c	Right				SD IN
	CD In(L)		t	Audio	Rec	Data(R)
	CD In(R)		o		Gain	ADC
			r
						Sample
			Σ			Rate	AC97
						Gen.
			/Mixer				Link	Audio
SPDIF							I/F	Controller
			(L)			PB
					PB	Data(L)
	HPOut L	S	(L)		Gain	DAC
Analog						EQ
								SD Out
		E
Output	HPOut R		(R)			PB
		L
Circuits
			(R)		PB	Data(R)
						DAC
					Gain
						EQ

Figure 5-13. AD1981B Audio Codec Functional Block Diagram

All inputs and outputs are two-channel stereo except for the microphone input, which is inputted as a single-channel but mixed internally onto both left and right channels. The microphone input is the default active input. All block functions are controlled through index-addressed registers of the codec.

5-32 361834-002 Technical Reference Guide