Atmel AT85DVK-07 Spezifikationen PDF herunterladen (Seite 155)

155

AT85C51SND3Bx

7632A–MP3–03/06

Table 157. Audio Codec Output Gain

Output Drive Control Output buffers can operate in two modes depending on the power supply voltage. These

are low impedance or high impedance modes. The low impedance mode is only avail

able in high power supply configuration and allows to drive a typical 32 Ω stereo

headphone, while the high impedance mode is available in low or high voltage power

supply configurations and allows to drive a typical 50 KΩ stereo amplifier. Control is

done by setting or clearing AODRV bit in ACCON according to

Table 158.

Table 158. Audio Codec Output Drive Selection

Audio Inputs The audio input system is based on a single sigma-delta A/D converter provided for

mono recording. It is enabled by setting the AIEN bit in ACCON.

Audio input system features are detailed in the following sections.

Inputs Sources The audio input source can come from either an electret type microphone input or the

stereo lines inputs sources. The selection of the source is done by setting or clearing the

AISSEL bit in ACCON according to

Table 159. When line inputs are selected as audio

input source, stereo channels are combined together in a mono signal prior to feed the

preamplifier.

Table 159. Audio Codec Input Source Selection

Audio Input Preamplifier Gain The signals coming from audio inputs goes through a preamplifier to adapt levels prior

to feed the A/D converter.The preamplifier gain is controlled by AIPG2:0 bits in ACIPG

according to

Table 160.

Table 160. Audio Codec Input Preamplifier Gain

AORG4:0

AOLG4:0

Gain Value

AORG4:0

AOLG4:0

Gain Value

AORG4:0

AOLG4:0

Gain Value

00000 6 dB 00111 -8 dB 01110 -22 dB

00001 4 dB 01000 -10 dB 01111 -24 dB

00010 2 dB 01001 -12 dB 10000 -26 dB

00011 0 dB 01010 -14 dB 10001 -28 dB

00100 -2 dB 01011 -16 dB 10010 -30 dB

00101 -4 dB 01100 -18 dB ≥ 10011 Mute

00110 -6 dB 01101 -20 dB

AODRV Drive Selection

0 Low/high voltage 50 KΩ drive

1 High voltage 32 Ω drive

AISSEL Selection

0 Line Inputs

1 Microphone Input

AIPG2:0 Gain Value AIPG2:0 Gain Value AIPG2:0 Gain Value

000 0 dB 010 +12 dB 100 +24 dB

1 2 ... 150 151 152 153 154 155 156 157 158 159 160 ... 262 263

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