Rainbow Electronics AT73C246 - Manual (Page 63)

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11050A–PMAAC–07-Apr-10
AT73C246
• INPUT_CONTROL (0x1E)
• OUTPUT_CONTROL (0x1F)
• INPUT_MIXER (0x20)
Like in the automatic path configuration, the audio controller will sequence audio codec sub-
functions ON/OFF as well as gain stepping. However, the audio path is no more selected via the
"PATHSEL" value in register AUTOSTART.
To specify a custom audio path:
• The bit CUSTCONF in register AUDIO_CONTROL (0x11) must be set to '1' to specify the
'custom' path configuration mode.
• The registers INPUT_CONTROL (0x1E), OUTPUT_CONTROL (0x1F), and INPUT_MIXER
(0x20) are set to define the audio path,
• The bit ENCONF in register AUDIO_CONTROL (0x11) is pulsed to '1' to enable the audio
controller sequencing.
Notes: 1. “Pulsed to ‘1’ ”means written to ‘1’ and then written to ’0’.
2. In this mode, the STANDBY bit behaves like in the automatic mode. It is possible to place the
CODEC in standby mode to reduce power consumption during audio pause by simply setting
the STANDBY bit to 1. STANDBY release is achieved by clearing this bit.
3. On-the-fly path change is achieved by modifying the registers INPUT_CONTROL (0x1E),
OUTPUT_CONTROL (0x1F) , and INPUT_MIXER (0x20) to define the new audio path config-
uration and then pulsing to '1' the ENCONF bit. In this case, a channel may be temporarily
(and smoothly) switched off and on to reach the new configuration.
4. Changing the three registers INPUT_CONTROL (0x1E), OUTPUT_CONTROL (0x1F) , and
INPUT_MIXER (0x20) with the ENCONF bit set to ‘1’ makes the changes to take effect imme-
diately. Therefore, the order of write operations is of prime importance. It is then recommended
to write these registers with ENCONF set to 0 and then pulse ENCONF to ‘1’ once the new
audio path is fully specified. Knowing the final state to reach, the audio controller is able to
sequence the controls with the right order and timings to ensure noise-free operation.
5. In this custom mode, the Audio Controller may forbid any configuration that does not make
sense. For example, it will prevent the headphone amplifier from being switched on if it has no
input source (DAC, Microphone, or Line).
6. It is possible and sometimes convenient to switch from an automatically set path to a custom
one. In this case, the audio controller softly performs the required path change. However, acti-
vating an automatic path configuration from a current custom path configuration is not allowed.
The audio codec must be switched off first (ENAC=0).
A software example of audio codec control using custom path control is provided in the section
“Basic Audio Codec Setting Using Custom Path Control” on page 135 .
12.5 Audio Codec Power Consumption Versus Programmed Audio Path
Unless otherwise specified:
• A
VDD
= 3.3V
• MCLK = 12.288MHz , FS = 48KHz
• All Gains set to 0dB
• No audio signal
• T
A
= 25°C.
• Headphone amplifier set in AC coupling mode.