TLV320AIC27
STEREO AUDIO CODEC
SLAS253A – MARCH 2000 – REVISED SEPTEMBER 2000
27
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
reset register (index 00h)
Writing any value to this register performs a register reset, which causes all registers to revert to their default
values. Reading this register returns the ID code of the part to indicate modem support (not supported by the
TLV320AIC27) and a code for the type of 3D stereo enhancement.
The ID decodes the capabilities of the TLV320AIC27 based on the information in Table 8.
Table 8. Reset Register Function
BIT
FUNCTION
VALUE ON
TLV320AIC27
ID0
Dedicated mic PCM in channel
0
ID1
Modem line codec support
0
ID2
Bass and treble control
0
ID3
Simulated stereo (mono to stereo)
0
ID4
Headphone out support
0
ID5
Loudness (bass boost) support
0
ID6
18-bit DAC resolution
1
ID7
20-bit DAC resolution
0
ID8
18-bit ADC resolution
1
ID9
20-bit ADC resolution
0
SE4...SE0
3D-stereo enhancement technique
11000
Note that the TLV320AIC27 defaults to indicate 18-bit compatibility. However, a control bit can be set in the
vendor-specific registers that changes bits ID6 and ID8 to be 0, indicating a 16-bit device. However, It is unlikely
that this function will be required, as the MSB justification of the ADC and DAC data means that a nominal 18-bit
device should be fully compatible with controllers that only provide 16-bit support. Most PC-type applications
only require 16-bit operation.
play master volume registers (index 02h, 04h and 06h)
These registers manage the output signal volumes. Register 02h controls the stereo master volume (both right
and left channels), register 04h controls the optional stereo headphone out, and register 06h controls the mono
volume output. Each step corresponds to 1.5 dB. The MSB of the register is the mute bit. When this bit is set
to 1, the level for that channel is set to –
∞ dB.
ML5 to ML0 are used for left channel level, MR5 to MR0 are used for right channel level, and MM5 to MM0 are
used for mono-out channel level.
Support for the MSB of the volume level is not provided by the TLV320AIC27. If the MSB is written to, then the
TLV320AIC27 detects when that bit is set and sets all four LSBs to 1s. For example, if the driver writes a 1xxxxx,
the TLV320AIC27 interprets that as x11111. It also responds when read with x11111 rather than 1xxxxx, the value
written to it. The driver can use this feature to detect if there is support for the 6th bit.
The default value of both the mono and the stereo registers is 8000h (1000 0000 0000 0000), which corresponds
to 0-dB gain with mute on.