Rainbow Electronics AT73C246 - Manual (Page 62)

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11050A–PMAAC–07-Apr-10
AT73C246
12.4.2.2 Pause Management With STANDBY Bit
To pause the audio codec activity and reduce power consumption to few hundreds of micro-
amps, the STANDBY bit can be activated in register AUTOSTART (0x10). The Audio codec will
then:
• Softly ramp down all the path concerned gains down-to mute and
• Power off all the audio sub-functions. The registers INPUT_CONTROL (0x1E),
OUTPUT_CONTROL (0x1F), and INPUT_MIXER (0x20) are modified by the audio
controller.
Notes: 1. Placing the codec in standby mode maintains the common mode voltage at VMID pin and thus
allows to re-start fastly,
2. Standby release is simply achieved by clearing the STANDBY bit (STANDBY = 0). The proce-
dure described in “STANDBY Release” on page 61 applies.
12.4.2.3 On-the-fly Path Change
The audio controller is able to softly switch from one audio path configuration to another without
shutting down the codec nor entering the STANDBY mode. As soon as it detects a change in the
PATHSEL value, the following mechanism occurs:
• Power up and/or power down of the audio sub-functions according to the final state to reach.
This operation generates automatic changes in the registers INPUT_CONTROL (0x1E),
OUTPUT_CONTROL (0x1F), and INPUT_MIXER (0x20).
• Ramp up and/or ramp down of the concerned path gain.
Notes: 1. A channel may be temporarily and smoothly switched off and on to reach the new path.
2. Any software write operation in the registers INPUT_CONTROL (0x1E), OUTPUT_CONTROL
(0x1F), and INPUT_MIXER (0x20) will generate a series of control on the audio codec sub-
functions. In automatic path control, the order of the write operations in those registers is of
prime importance. Please note that changing those registers updates the used audio path
without updating the PATHSEL value. Therefore, these write operations are not recommended
and must be limited to simple ones (for example changing LINESEL bit in register
INPUT_CONTROL (0x1E) ).
12.4.2.4 Audio Codec Shutdown
The Audio controller will start to shutdown the codec if ENAC = 0. The shutdown sequence is
made of the following steps:
• Softly ramp down all the path concerned gains down-to mute,
• Power off all the audio sub-functions and,
• Power off the common voltage VMID.
Notes: 1. In this mode, the power consumption is reduced to few hundreds of nA.
2. The common mode voltage power-off follows VMID time constant and thus may take a few
hundreds of milliseconds depending on VMID capacitor. See “Audio Codec Bias” on page
22.
A software example of audio codec control using automatic path control is provided in the sec-
tion
“Basic Audio Codec Setting Using Automatic Path Control” on page 134 .
12.4.3 Custom Path Configuration
In this custom path mode, the audio path control is managed by the following registers:
• AUTOSTART (0x10) (ENAC and STANDBY bits only)
• AUDIO_CONTROL (0x11) (ENCONF and CUSTCONF bits only)