CS5535 datasheet(84/555 Pages) NSC

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ACC Functional Description (Continued)

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Revision 0.8

4.3.4.2

AC Link Output Frame (AC_S_OUT)

The audio output frame data stream corresponds to the

time division multiplexed bundles of all digital output data

targeting the AC97 codec’s DAC inputs and control regis-

ters. Each audio output frame contains 13, 20-bit outgoing

data slots, except for slot 0, it has 16 bits. Slot 0 is a dedi-

cated slot used for the AC Link protocol.

An audio output frame begins with a low-to-high transition

of the AC_S_SYNC signal. AC_S_SYNC is synchronous to

the rising edge of AC_CLK. The AC97 codec samples the

AC_S_SYNC on the immediately following falling edge of

AC_CLK. AC_S_SYNC is held high for 16 bit clocks. The

ACC transmits data on each rising edge of the bit clock,

whereas the AC97 codec samples the data on the falling

edge of AC_CLK.

The serial output stream is MSB justified (MSB first) within

each slot, and all non-valid bit positions are stuffed with 0s

by the AC Link interface module.

Slot 0: TAG

This slot is used for AC Link protocol information. The first

bit (bit 15) flags the validity of the entire audio frame as a

whole. If this bit is 0, all of the remaining bits in the frame

should be 0. The next 12 bits indicate the validity of the 12

following slots. The last two bits contain the codec ID for

accessing registers of several codecs. When the codec ID

is 01, 10, or 11, bits 13 and 14 must always be 0, even if

slots 1 and 2 are valid. Slots that are marked invalid by slot

0 should be padded with all 0s (except for slots 1 and 2

while accessing registers of a secondary codec).

bit 15

Frame Valid

bit 14

Slot 1 Valid

(primary codec only)

bit 13

Slot 2 Valid

(primary codec only)

bits [12:3]

Slot 3-12 Valid bits

(bit[12] -> slot 3, bit[11] -> slot 4,

bit[10] -> slot 5, ... , bit[3] -> slot 12)

bit 2

Reserved

bits [1:0]

Codec ID field

Slot 1: Command Address

The command address is used to access registers within

the AC97 codec. The AC97 registers control features and

monitor status for AC97 codec functions, including mixer

settings and power management as indicated in the AC97

Codec specifications.

The control interface architecture supports up to 64 16-bit

read/write registers, addressable on even byte boundaries,

and reserves support for 64 odd addresses. Audio output

frame slot 1 communicates control register address, and

write/read command information to the AC97 codec.

bit 19

Read/Write Command

(1 = Read, 0 = Write)

bits [18:12]

Control Register Index

(64 16-bit locations, addressed on

even byte boundaries)

bits [11:0]

Reserved

(Stuffed with 0s)

The first bit (MSB) indicates whether the current control

transaction is a read or write operation. The following 7 bit

positions

communicate

the

targeted

control

address.

Slot 2: Command Data

The command data slot carries 16-bit control register write

data if the current command port operation is a write cycle

as indicated by slot 1, bit 19.

bits [19:4]

Control Register Write Data

(Stuffed with 0s if current operation

is a read)

bits [3:0]

Reserved

(Stuffed with 0s)

If the current command port operation is a read, then the

entire slot is stuffed with 0s.

Slot 3: PCM Playback Left Channel

Outputs the front left audio DAC data (main output) (16-bit

resolution, MSB first, unused LSBs = 0).

Slot 4: PCM Playback Right Channel

Outputs the front right audio DAC data (main output) (16-bit

resolution, MSB first, unused LSBs = 0).

Slot 5: Modem Line 1 DAC

Outputs the modem line 1 DAC data (16-bit resolution,

MSB first, unused LSBs = 0).

Slot 6: PCM Playback Center Channel

Outputs the center channel DAC data (16-bit resolution,

MSB first, unused LSBs = 0).

Slot 7: PCM Playback Left Surround Channel

Outputs the left surround channel DAC data (16-bit resolu-

tion, MSB first, unused LSBs = 0).

Slot 8: PCM Playback Right Surround Channel

Outputs the right surround channel DAC data (16-bit reso-

lution, MSB first, unused LSBs = 0).

Slot 9: PCM Playback LFE Channel

Outputs the low frequency effects channel DAC data (16-bit

resolution, MSB first, unused LSBs = 0).

Slot 10: Not used

Slots 10 is not used by the ACC.

Slot 11: Modem Headset DAC

Outputs the headset DAC data (16-bit resolution, MSB first,

unused LSBs = 0).

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