LM4550 datasheet(17/25 Pages) NSC

17 / 25 page

Application Information (Continued)

Bit

Description

Comment

Valid Frame

1 = This frame has valid

data.

Control register

address

1 = Control Address is

valid.

Control register

data

1 = Control Data is valid.

Left Playback

PCM Data

1 = Left PCM Data is valid.

Right Playback

PCM Data

1 = Right PCM Data is

valid.

PCM Center

1 = Center PCM Data is

valid.

PCM Left

Surround

1 = PCM Left Surround is

valid.

PCM Right

Surround

1 = PCM Right Surround is

valid.

PCM LFE

1 = PCM LFE is valid.

SDATA_OUT Slot 1: Control Address

Slot 1 is used both to write to the LM4550 registers as well

as read back a register’s current value. The MSB of Slot 1

(bit 19) signifies whether the current control operation is a

read or a write. Bits 18 through 12 are used to specify the

significant twelve bits are reserved and should be stuffed

with zeros by the AC’97 controller.

Bits

Description

Comment

Read/Write

1 = Read,0=Write

18:12

Control

Identifies the Control

11:0

Reserved

Set to "0"

SDATA_OUT Slot 2: Control Data

Slot 2 is used to transmit 16 bit control data to the LM4550 in

the event that the current operation is a write operation. The

least significant four bits should be stuffed with zeros by the

AC ’97 controller. If the current operation is a register read,

the entire slot, bits 19 through 0 should be stuffed with zeros.

Bits

Description

Comment

19:4

Control

Data

Set bits to "0" if read

operation

3:0

Reserved

Set to "0"

SDATA_OUT Slot 3 and 4: PCM Playback Left , Right

Channel

Bits

Description

Comment

19:0

PCM Audio

Data for Left

/RightDACs

Set unused bits to "0"

Slot 3 and 4 are 20 bit fields used to transmit data intended

for the left/right DACs on the LM4550. Any unused bits

should be padded with zeros. The LM4550 DAC’s have 18

bit resolution and thus will use the first 18 bits of the 20 bit

PCM stream.

SDATA_OUT Slot 7 and 8: PCM Playback Left/Right

Surround

Bits

Description

Comment

19:0

PCM Audio

Data for

Left/Right

Surround

Set unused bits to "0"

SDATA_OUT Slot 6 and 9: PCM Playback Center/LFE

Bits

Description

Comment

19:0

PCM Audio

Data for

Center/

LFESurround

Set unused bits to "0"

SDATA_OUT Slots 5, 10–12: Reserved

Set these SDATA_OUT slots to "0" as they are not currently

implemented and are reserved for future use.

10097208

FIGURE 6. AC Link Audio Input Frame

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