Rainbow-electronics AT73C246 Manual do Utilizador descarregar pdf (Página 61)

11050A–PMAAC–07-Apr-10

AT73C246

master clock must be running to properly shutdown the codec. This time linearly varies with

ASR_TIME value. See Table 12-1

The analog power-off time corresponds to the VMID’s discharge time specified in “Audio Codec

Bias” on page 22: T

MID_OFF

Finally, the wait step #8 in “Audio Codec Typical Control Sequence” on page 57 needs to acco-

modate the digital power-off time + the analog power-off time.

12.4.2 Automatic Path Configuration

In this automatic path mode, the audio path control is fully managed by the AUTOSTART(0x10)

• ENAC (Enable Audio codec),

• STANDBY

(1)

(Audio standby) and

• PATHSEL (Audio path selection).

When the audio controller detects a change in these bits, it generates sequential controls to the

audio codec sub-functions (power-up, gain ramping, unmute,…) with the right timing and order.

Notes: 1. Audio STANDBY does not refer to the PMU STANDBY state as defined in “AT73C246 Power

Manager Functional State Diagram” on page 25. The audio STANDBY mode activated by reg-

ister AUTOSTART (0x10) only refers to the audio codec controller.

12.4.2.1 STANDBY Release

Once the CODEC is started and in standby mode (ENAC=1 and STANDBY=1, step #5 in “Audio

Codec Typical Control Sequence” on page 57), the audio path is simply selected by PATHSEL

bits.

At STANDBY release (STANDBY=0), the audio controller will:

• Power-up the requested audio sub-functions. To do so, the audio controller makes WRITE

accesses to the registers

– INPUT_CONTROL (0x1E),

– OUTPUT_CONTROL (0x1F) and

– INPUT_MIXER (0x20).

• Ramp-up the concerned path gains from mute to their current register value.

Notes: 1. Changing PATHSEL value with STANDBY=1 does not changes the codec state. It remains in

STANDBY mode.

2. The audio controller always ensures minimum power consumption by powering only needed

sub-functions.

3. Audio parameters (volume, mute, effects…) can be modified before or after releasing the

standby mode.

Table 12-1. Audio Codec Maximum Power-off Time

ASR_TIME Power-off time (ms)

00 375

01 750

10 1500

11 3000

1 2 ... 56 57 58 59 60 61 62 63 64 65 66 ... 158 159

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