lm4550 National Semiconductor Corporation, lm4550 Datasheet - Page 17

• Manufacturer Part Number: lm4550
• Description: Ac ?97 Rev 2.1 Multi-channel Audio Codec With Stereo Headphone Amplifier, Sample Rate Conversion And National 3d Sound
• Manufacturer: National Semiconductor Corporation

Application Information
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
register address of the read or write operation. The least
significant twelve bits are reserved and should be stuffed
with zeros by the AC’97 controller.
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
18:12
Bits
11:0
Bit
15
14
13
12
11
19
9
8
7
6
Control register
Control register
Right Playback
Left Playback
PCM Center
Description
Valid Frame
Description
PCM Right
Read/Write
PCM Data
PCM Data
PCM LFE
PCM Left
Reserved
Surround
Surround
Register
address
Control
data
1 = Left PCM Data is valid.
1 = PCM Right Surround is
1 = PCM Left Surround is
1 = Control Data is valid.
1 = This frame has valid
1 = Center PCM Data is
1 = Right PCM Data is
1 = Control Address is
1 = PCM LFE is valid.
Identifies the Control
1 = Read, 0 = Write
Comment
Comment
Set to "0"
Register
valid.
valid.
valid.
valid.
valid.
data.
(Continued)
FIGURE 6. AC Link Audio Input Frame
17
AC ’97 controller. If the current operation is a register read,
the entire slot, bits 19 through 0 should be stuffed with zeros.
SDATA_OUT Slot 3 and 4: PCM Playback Left , Right
Channel
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
SDATA_OUT Slot 6 and 9: PCM Playback Center/LFE
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.
Bits
19:4
Bits
19:0
Bits
19:0
Bits
19:0
3:0
Register Write
LFESurround
Data for Left
Description
Description
Description
Description
/RightDACs
PCM Audio
PCM Audio
PCM Audio
Reserved
Left/Right
Surround
Data for
Data for
Control
Center/
Data
Set unused bits to "0"
Set unused bits to "0"
Set unused bits to "0"
Set bits to "0" if read
Comment
Comment
Comment
Comment
Set to "0"
operation
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