Audio Codec '97

AC ‘97 Component Specification Revision 2.3 Rev 1.0
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5.8.5 S/PDIF Control Register (Index 3Ah)
Reg Name D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 Default
3Ah S/PDIF Control V DRS SPSR1 SPSR0 L CC6 CC5 CC4 CC3 CC2 CC1 CC0 PRE COPY /AUDIO PRO 2000h
Register 3Ah is a read/write register that controls S/PDIF functionality and manages bit fields propagated as channel
status (or subframe in the V case). With the exception of V, this register should only be written to when the S/PDIF
transmitter is disabled (SPDIF bit in Register 2Ah is "0"). This ensures that control and status information start up
correctly at the beginning of S/PDIF transmission.
V Validity: This bit affects the “Validity flag”, bit<28> transmitted in each subframe, and enables the S/PDIF
transmitter to maintain connection during error or mute conditions. The behavior of the S/PDIF transmitter with
respect to this bit depends on the value of the VCFG bit in the Extended Audio Status and Control register. The
behavior of the transmitter is defined in the definition of the Extended Audio Status and Control Register (Index
2Ah), section 5.8.2.
DRS Double Rate S/PDIF: This bit controls support for optional higher sample rate transmission. When DRS is
enabled “1” and SPSA is configured {“01”, “10”, or “11”} the S/PDIF transmitter uses AC-link slots 3&4 + {7&8,
6&9, or 10&11} to supply data at Fs = 64, 88.2 or 96 kHz. The SPCV bit must indicate a valid configuration. A
DRS capable Codec must automatically determine the correct channel status bits for Fs from DRS and SPSR and
insert them as necessary. The Controller or Driver must perform write followed by read to determine if DRS is
supported.
SPSR[1,0] S/PDIF Sample Rate: This field controls the S/PDIF transmitter clock rate (64*Fs unless DRS is
enabled). The Controller or Driver must perform write followed by read to determine if the optional 32 and 44.1 kHz
rates are supported.
• SPSR[1:0] = “00”, sample rate set to 44.1kHz (optional)
• SPSR[1:0] = “01”, reserved
• SPSR[1:0] = “10”, sample rate set to 48 kHz [default]
• SPSR[1:0] = “11”, sample rate set to 32 kHz (optional)
L Generation Level: programmed according to IEC standards, or as appropriate
CC[6-0] Category Code: programmed according to IEC standards, or as appropriate
PRE Preemphasis: "1" indicates filter preemphasis is 50/15 µsec, "0" preemphasis is none.
COPY Copyright: "1" indicates copyright is asserted, "0" copyright is not asserted.
/AUDIO Non-Audio: "1" indicates data is non PCM format, "0" data is PCM.
PRO Professional: "1" indicates Professional use of channel status, "0" Consumer.