The Codec Identity is determined by the inverting input pins

ID1#, ID0# (pins 46 and 45) and can be read as the value of

the ID1, ID0 bits (D15, D14) in the Extended Audio ID

register, 28h of the target codec.

In addition to the Codec Identity bits (ID1, ID0), the read-only

Extended Audio ID register (28h) contains the AMAP bit

(D9). The AMAP bit indicates support for the (optional) AC

’97 Rev. 2.1 compliant mappings from slots in AC Link Out-

put Frames to the audio DACs for each of the four Codec

Identity modes. AMAP = 1 indicates that the default mapping

(as realized after reset) of Slots-to-DACs conforms to Table

1. Slots in AC Link Input Frames are always mapped such

that PCM data from the left ADC channel is carried by slot 3

and PCM data from the right ADC channel by slot 4. Output

Frames are those carried by the SDATA_OUT signal from

the controller to the codec while Input Frames are those

carried by the SDATA_IN signal from the codec to the

controller.

SLOT 0: TAG bits in Output Frames (controller to codec)

Bit 15

14

13

12

11

10

987654321

0

Valid

Frame

Slot 1

Valid

Slot 2

Valid

Slot 3

Valid

Slot 4

Valid

X

Slot 6

Valid

Slot 7

Valid

Slot 8

Valid

Slot 9

Valid

XXXX

ID1

ID0

Extended Audio ID register (28h): Support for Multiple Codecs

Reg

Name

D15 D14 D13 D12 D11 D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

Default

28h

Extended

Audio ID

ID1

ID0

XXXX

AMAP

XXXXXXXX

VRA

X201h

TABLE 1. AMAP Slot-to-DAC Audio MAPping

Codec Identity

Mode

ID1

(D15, 28h)

ID0

(D14, 28h)

Left DAC data

Right DAC data

From Slot #

5.1 Audio channel

(Note 11)

From Slot #

5.1 Audio channel

(Note 11)

Primary

0

0

3

Left

4

Right

Secondary 1

0

1

3

Left

4

Right

Secondary 2

1

0

7

Left Surround

8

Right Surround

Secondary 3

1

1

6

Center

9

LFE

Note 11: AC ’97 Rev 2.1 specifies this allocation of 5.1 Audio channels to these slots in the AC Link Output Frame

www.national.com

28