Datasheet

LM4549B

www.ti.com

SNAS598A –JULY 2012–REVISED MAY 2013

When reading from a Secondary Codec, the controller must send the correct Codec ID bits (i.e. the target Codec

Identity in slot 0, bits 1 and 0) along with the read-request bit (slot 1, bit 19) and target register address (slot 1,

bits 18 – 12). To write to a Secondary Codec, a controller must send the correct Codec ID bits when slot 1

contains a valid target register address and “write” indicator bit and slot 2 contains valid target register data. A

write operation is only valid if the register address and data are both valid and sent within the same frame. When

accessing the Primary Codec, the Codec ID bits are cleared and the tag bits 14 and 13 resume their role

indicating the validity of Command Address and Data in slots 1 and 2.

The use of the tag bits in Input Frames (carried by the SDATA_IN signal) is the same for Primary and Secondary

Codecs.

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.

Slots in the AC Link Output Frame are always mapped to carry data to the left DAC channel in slot 3 and data to

the right DAC channel in slot 4. Similarly, 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 9 8 7 6 5 4 3 2 1 0

Valid Slot 1 Slot 2 Slot 3 Slot 4

X X X X X X X X X ID1 ID0

Frame Valid Valid Valid Valid

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

Extended

28h ID1 ID0 X X X X X X X X X X X X X VRA X001h

Audio ID

Product Folder Links: LM4549B