wm9704m Wolfson Microelectronics plc, wm9704m Datasheet - Page 20

• Manufacturer Part Number: wm9704m
• Description: Amc97 Audio Modem Codec
• Manufacturer: Wolfson Microelectronics plc

WM9704M
WOLFSON MICROELECTRONICS LTD
COMMAND ADDRESS PORT BIT ASSIGNMENTS
The first bit (MSB) sampled by the WM9704M indicates whether the current control transaction is a
read or write operation. The following 7 bit positions communicate the targeted control register
address. The trailing 12 bit positions within the slot are reserved and must be stuffed with 0s by the
AC’97 controller.
SLOT 2: COMMAND DATA PORT
The command data port is used to deliver 16-bit control register write data in the event that the
current command port operation is a write cycle. (As indicated by slot 1, bit 19).
If the current command port operation is a read then the entire time slot must be stuffed with 0s by
the AC’97 controller.
SLOT 3: PCM PLAYBACK LEFT CHANNEL
Audio output frame slot 3 is the composite digital audio left playback stream. In a typical ‘Games
Compatible’ PC this slot is composed of standard PCM (.wav) output samples digitally mixed (on the
AC’97 controller or host processor) with music synthesis output samples. If a sample stream of
resolution less than 20-bits is transferred, the AC’97 controller must stuff all trailing non-valid bit
positions within this time slot with 0s.
SLOT 4: PCM PLAYBACK RIGHT CHANNEL
Audio output frame slot 4 is the composite digital audio right playback stream. In a typical ‘Games
Compatible’ PC this slot is composed of standard PCM (.wav) output samples digitally mixed (on the
AC’97 controller or host processor) with music synthesis output samples.
If a sample stream of resolution less than 20-bits is transferred, the AC’97 controller must stuff all
trailing non-valid bit positions within this time slot with 0s.
SLOT 5: OPTIONAL MODEM LINE 1 CODEC
Audio output frame slot 5 contains the MSB justified modem line1 DAC input data. This optional
AC’97 feature is supported in WM9704M, but only in the modem operation mode (selected with the
mode0/1 pins). If data is written to this location it is applied to the rear channel DACs if the modem
mode is enabled. This may be determined by the AC’97 controller interrogating the WM9704M
Vendor ID registers; if modem mode is disabled, the device appears not to support modem. If the
mode is enabled, the modem support flag is set.
SLOTS 6 TO 9: SURROUND SOUND DATA
Audio output frame slots 6 to 9 are used to send surround sound data to extra DAC channels. These
slots are supported by WM9704M in Revision 2.1 and modem modes. Note that the data in the
surround sound slots will only be applied to the front DAC. The slots used depend on the Codec ID
configuration (see Table 7).
SLOT 10: OPTIONAL MODEM LINE2 CODEC
Audio output frame slot 10 contains MSB justified modem Line2 DAC input data. This optional AC’97
feature is supported by WM9704M, but only when register 5Ah DLM (Dual line modem) is set.
SLOT 11: HANDSET DAC
Slot 11 is not supported.
Bit (19)
Bit (18:12)
Bit (11:0)
Bit (19:4)
Bit (3:0)
Read/write command (1 = read, 0 = write)
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)
PD Rev 3.2 January 2001
Production Data
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