AD1985

Rev. A | Page 43 of 48

Function Select Register (Index 0x66, Page 01)

Reg Num

Name

D15

D14

D13

D12

D11

D10

D9 D8 D7 D6 D5 D4

D3

D2

D1

D0

Default

0x66

Function Select

X

X

X

X

X

X

X

X

X

X

X

FC3 FC2 FC1 FC0 T/R 0x0000

New register added for AC ’97 2.3.

Function Code Bits. (Default 0.) These bits specify the type of audio function described by this page.

0x00: DAC 1 (Master Out). Maps to line out L/R, codec Pins 35 and 36.

0x01: DAC 2 (AUX Out). Maps to surround/HP out L/R, codec Pins 39 and 41.

0x02: DAC 3 (Center/LFE). Maps to center/LFE, codec Pins 31 and 32.

0x03: S/P-DIF Out.

0x04: Phone In.

0x05: Mic 1 (Mic Select = 0).

0x06: Mic 2 (Mic Select = 1).

0x07: Line In.

0x08: CD In.

0x09: Video In.

0x0A: Aux In.

0x0B: Mono Out

0x0C to 0x0F: Reserved.

FC[3:0]

These bits are read/write and represent current AC ’97 2.3 defined I/O capabilities. Software will program the corresponding

I/O number in this field together with the tip/ring selector bit T/R. Once software programs the value and properly reads it

back to confirm selection and implementation, it will access the rest of the bit fields in the descriptor. A read-only value of 0

in this register, along with a read-only value of 0 in the IV (Register 0x68 page 01) bit, indicates the codec does not support

the information and I/O register.

Tip or Ring Selection Bit. (Default is 0.)

This bit sets which jack conductor the sense value is measured from. Software will program the corresponding ring/tip

selector bit together with the I/O number in Bits FC[3:0]. Once software programs the value and properly reads it back to

confirm selection and implementation, it will access the rest of the bit fields in the descriptor.

0: Tip

1: Ring

T/R

Mono inputs and outputs report the relevant function and sense information when T/R is set to 0 (tip).