wm9708 Wolfson Microelectronics plc, wm9708 Datasheet - Page 19

• Manufacturer Part Number: wm9708
• Description: Ac?97 Revision 2.1 Audio Codec
• Manufacturer: Wolfson Microelectronics plc

Production Data
AC-LINK AUDIO INPUT FRAME (SDATA_IN)
Figure 11 AC-link Audio Input Frame
w
SDATAIN
BITCLK
SYNC
END OF PREVIOUS
AUDIO FRAME
CODEC
READY
12.288MHz
TAG PHASE
SLOT(1)
SLOTS 6 TO 9: SURROUND SOUND DATA
Audio output frame slots 6 to 9 are used to send surround sound data. Unsupported by WM9708.
SLOTS 10 AND 11: LINE2 AND HANDSET DAC
These data slots are not supported.
SLOT 12: GPIO CONTROL
These data slots are not supported.
The audio input frame data streams correspond to the multiplexed bundles of all digital input data
targeting the AC’97 controller. As is the case for audio output frame, each AC-link audio input frame
consists of 12, 20-bit time slots plus the tag slot.
Slot 0 is a special reserved time slot containing 16-bits, which are used for AC-link protocol
infrastructure.
Within slot 0 the first bit is a global bit (SDATAIN slot 0, bit 15) which flags whether the WM9708 is in
the Codec Ready state or not. If the Codec Ready bit is a 0, this indicates that the WM9708 is not
ready for normal operation. This condition is normal following the desertion of power on reset for
example, while the WM9708’s voltage references settle. When the AC-link Codec Ready indicator bit
is a 1, it indicates that the AC-link and the WM9708 control and status registers are in a fully
operational state. The AC’97 controller must further probe the Powerdown Control/Status Register to
determine exactly which subsections, if any, are ready.
Prior to any attempts at putting the WM9708 into operation the AC’97 controller should poll the first
bit in the audio input frame (SDATAIN slot 0, bit 15) for an indication that the WM9708 has gone
Codec Ready.
Once the WM9708 is sampled Codec Ready then the next 12 bit positions sampled by the AC’97
controller indicate which of the corresponding 12 time slots are assigned to input data streams, and
that they contain valid data. Figure 11 illustrates the time slot based AC-link protocol.
There are several subsections within the WM9708 that can independently go busy/ready. It is the
responsibility of the WM9708 controller to probe more deeply into the WM9708 register file to
determine which the WM9708 subsections are actually ready.
SLOT(2)
('1' = TIME SLOT CONTAINS
81.4nS
TIME SLOT 'VALID' BITS
VALID PCM DATA)
SLOT(12)
'0'
'0'
'0'
19
SLOT (1)
0
19
20.8μS (48kHz)
DATA PHASE
SLOT (2)
0
19
SLOT (3)
0
PD, Rev 4.2, August 2009
19
SLOT (12)
WM9708
0
19