Samsung S3C2451X User Manual page 695

S3C2451 RISC MICROPROCESSOR
AC-LINK DIGITAL INTERFACE PROTOCOL
Each AC97 Codec incorporates a five-pin digital serial interface that links it to the S3C2451 AC97 Controller.
AC-link is a full-duplex, fixed-clock, PCM digital stream. It employs a time division multiplexed (TDM) scheme to
handle control register accesses and multiple input and output audio streams. The AC-link architecture divides
each audio frame into 12 outgoing and 12 incoming data streams. Each stream has 20-bit sample resolution and
requires a DAC and an analog-to-digital converter (ADC) with a minimum 16-bit resolution.
Slot #
0
SYNC TAG
Phase
SDATA_OUT
TAG
SDATA_IN
TAG
Figure 27-4 shows the slot definitions that the S3C2451 AC97 Controller supports. The S3C2451 AC97
Controller provides synchronization for all data transaction on the AC-link.
A data transaction is made up of 256 bits of information broken up into groups of 13 time slots and is called a
frame. Time slot 0 is called the Tag Phase and is 16 bits long. The other 12 time slots are called the Data Phase.
The Tag Phase contains one bit that identifies a valid frame and 12 bits that identify the time slots in the Data
Phase that contain valid data. Each time slot in the Data Phase is 20 bits long. A frame begins when SYNC goes
high. The amount of time that SYNC is high corresponds to the Tag Phase. AC97 frames occur at fixed 48 kHz
intervals and are synchronous to the 12.288 MHz bit rate clock, BITCLK. The controller and the Codec use the
SYNC and BITCLK to determine when to send transmit data and when to sample received data. A transmitter
transitions the serial data stream on each rising edge of BITCLK and a receiver samples the serial data stream on
falling edges of BITCLK. The transmitter must tag the valid slots in its serial data stream. The valid slots are
tagged in slot 0. Serial data on the AC-link is ordered most significant bit (MSB) to least significant bit (LSB). The
Tag Phase's first bit is bit 15 and the first bit of each slot in Data Phase is bit 19. The last bit in any slot is bit 0.
1 2 3
CMD CMD PCM
LEFT
ADDR DATA
STATUS STATUS PCM
ADDR DATA LEFT
Figure 27-4. Bi-directional AC-link Frame with Slot Assignments
Preliminary product information describe products that are in development,
for which full characterization data and associated errata are not yet available.
Specifications and information herein are subject to change without notice.
4 5 6
Data
Phase
PCM
RSRVD RSRVD RSRVD
RIGHT
PCM PCM
RSRVD RSRVD
MIC
RIGHT
7 8 9 10
RSRVD RSRVD RSRVD
RSRVD RSRVD RSRVD
AC97 CONTROLLER
11 12
RSRVD RSRVD
RSRVD RSRVD
27-5