cs5535 National Semiconductor Corporation, cs5535 Datasheet - Page 84

• Manufacturer Part Number: cs5535
• Description: Geode Cs5535 Companion Multi-function South Bridge
• Manufacturer: National Semiconductor Corporation

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ACC Functional Description
4.3.4.2
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
bit 14
bit 13
bits [12:3]
bit 2
bits [1:0]
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
AC Link Output Frame (AC_S_OUT)
Frame Valid
Slot 1 Valid
(primary codec only)
Slot 2 Valid
(primary codec only)
Slot 3-12 Valid bits
(bit[12] -> slot 3, bit[11] -> slot 4,
bit[10] -> slot 5, ... , bit[3] -> slot 12)
Reserved
Codec ID field
Read/Write Command
(1 = Read, 0 = Write)
(Continued)
84
bits [18:12]
bits [11:0]
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 register
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]
bits [3:0]
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).
Control Register Index
(64 16-bit locations, addressed on
even byte boundaries)
Reserved
(Stuffed with 0s)
Control Register Write Data
(Stuffed with 0s if current operation
is a read)
Reserved
(Stuffed with 0s)
Revision 0.8