cs4297 Cirrus Logic, Inc., cs4297 Datasheet - Page 19

• Manufacturer Part Number: cs4297
• Description: Crystalclear Soundfusion Audio Codec 97 Logic
• Manufacturer: Cirrus Logic, Inc.

DS242F5
Slot 1: Read-Back Address Port
Slot 1 is the Read-Back Address Port. The Read-Back Address Port is used to echo the AC’97 Register
address back to the AC’97 Controller when the CS4297 has been issued a read request from the previous
frame. Included only for historical purposes, this address may be used by the AC’97 Controller to synchro-
nize read accesses. The CS4297 will only echo the register index for a read access. Write accesses will not
return valid data in Slot 1. The 20 bits of this slot are defined as:
RI6 - RI0 - Bits 18-12 contain the 7-bit register index to the AC’97 Registers in the CS4297.
All other undefined bits in Slot 1 will be returned by the CS4297 ‘cleared’.
Slot 2: Read-Back Data Port
Slot 2 is the Read-Back Data Port. The Read-Back Data Port contains the register data requested by the
AC’97 Controller from the previous read request. It reflects the valid data bits from the 16-bit AC’97 Reg-
ister being read. All read requests will return read addresses and data on the following serial data frame.
The 20 bits of this slot are defined as:
WD15 - WD0 - Bits 19-4 contain the 16-bit AC’97 Register value returned to the AC’97 Controller by the
CS4297. Bits 3-0 are undefined in Slot 2 and will be returned by the CS4297 ‘cleared’.
NOTE: The CS4297 implements bus-keeper logic for its 16-bit registers. Any read accesses from AC’97
Registers with undefined bits may return a ‘set’ or ‘clear’ value. The value returned depends on the state
of that bit location from the previous access. No AC’97 Controller software dependencies should exist on
the value of undefined AC’97 Register bits. For a list of the undefined bits in the AC’97 register map, see
Table 2, Mixer Registers.
Slot 3: Left Channel PCM Capture Data
Slot 3 contains the left channel data. The 20 bits of this slot are defined as:
LP17 - LP0 - This is the 18-bit PCM 2’s compliment capture data from the left channel ADC in the
CS4297. The PCM capture data is left justified in the most significant 18 of the 20 bits in the slot.
The least significant 2 bits will be ‘cleared’.
Bit 19 18
Bit 19 18
RD15 RD14 RD13 RD12 RD11 RD10 RD9 RD8 RD7 RD6 RD5 RD4 RD3 RD2 RD1 RD0
Bit 19 18
CS4297
CrystalClear™ SoundFusion™ Audio Codec ’97
LP17 LP16 LP15 LP14 LP13 LP12 LP11 LP10 LP9 LP8 LP7 LP6 LP5 LP4 LP3 LP2 LP1 LP0
F16
F36
F56
0
F17
F37
F57
RI6
F18
F38
F58
RI5
17
17
17
F19
F39
F59
RI4
16
16
16
F20
F40
F60
RI3
15
15
15
F21
F41
F61
RI2
14
14
14
F22
F42
F62
RI1
13
13
13
F23
F43
F63
RI0
12
12
12
F24
F44
F64
11
11
11
0
F25
F45
F65
10
10
10
0
F26
F46
F66
9
0
9
9
F27
F47
F67
8
0
8
8
F28
F48
F68
7
0
7
7
F29
F49
F69
6
0
6
6
F30
F50
F70
5
0
5
5
F31
F51
F71
4
0
4
4
F32
F52
F72
3
0
3
0
3
F33
F53
F73
2
0
2
0
2
F34
F54
F74
1
0
1
0
1
0
F35
F55
F75
0
0
0
0
0
0
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