Datasheet

BIT_CLK
SDATA_OUT
SYNC
LM4549B samples
SYNC assertion
LM4549B samples
first bit of SDATA_OUT
End of previous
Audio Frame
Valid
Frame
Slot
(1)
Slot
(2)
LM4549B
SNAS598A –JULY 2012–REVISED MAY 2013 www.ti.com
Figure 19. Start of AC Link Output Frame
Table 1. Slot 0, Output Frame
Bit Description Comment
15 Valid Frame 1 = Valid data in at least one slot.
14 Control register address 1 = Valid Control Address in Slot 1 (Primary codec only)
13 Control register data 1 = Valid Control Data in Slot 2 (Primary codec only)
1 = Valid PCM Data in Slot 3
12 Left DAC data in Slot 3
(Primary & all Secondary modes)
1 = Valid PCM Data in Slot 4
11 Right DAC data in Slot 4
(Primary & all Secondary modes)
10:2 Not Used Controller should stuff these slots with “0”s
Codec ID The codec ID is used in a multi-codec system to identify the target Secondary
1,0
(ID1, ID0) codec for the Control Register address and/or data sent in the Output Frame
SDATA_OUT: Slot 1 – Read/Write, Control Address
Slot 1 is used by a controller to indicate both the address of a target register in the LM4549B and whether the
access operation is a register read or register write. The MSB of slot 1 (bit 19) is set to 1 to indicate that the
current access operation is 'read'. Bits 18 through 12 are used to specify the 7-bit 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.
Table 2. Slot 1, Output Frame
Bits Description Comment
1 = Read
19 Read/Write
0 = Write
18:12 Register Address Identifies the Status/Command register for read/write
11:0 Reserved Controller should set to "0"
SDATA_OUT: Slot 2 – Control Data
Slot 2 is used to transmit 16-bit control data to the LM4549B when the access operation is 'write'. The least
significant four bits should be stuffed with zeros by the AC '97 controller. If the access operation is a register
read, the entire slot, bits 19 through 0 should be stuffed with zeros.
Table 3. Slot 2, Output Frame
Bits Description Comment
19:4 Control Register Write Data Controller should stuff with zeros if operation is “read”
3:0 Reserved Set to "0"
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