wm9714l Wolfson Microelectronics plc, wm9714l Datasheet - Page 26

• Manufacturer Part Number: wm9714l
• Description: Ac?97 Audio Codec
• Manufacturer: Wolfson Microelectronics plc

WM9714L
PCM INTERFACE
w
OPERATION
WM9714L can implement a PCM voice codec function using the dedicated VXDAC and either one or
both of the existing hi-fi ADC’s. In PCM codec mode, VXDAC input and ADC output are interfaced
via a PCM style port via GPIO pins.
This interface can support one ADC channel, or stereo/dual ADC channels if required, (two channels
of data are sent per PCM frame as back to back words).
In voice only mode, the AC link is used only for control information, not audio data. Therefore it will
generally be shut down (PR4=1), except when control data must be sent.
The PCM interface makes use of 4 of the GPIO interface pins, for clock, frame, and data in/out. If the
PCM codec function is not enabled then the GPIO pins may be used for other functions.
INTERFACE PROTOCOL
The WM9714L PCM audio interface is used for the input of data to the Voice DAC and the output of
data from the Stereo ADC. When enabled, the PCM audio interface uses four GPIO pins:
Depending on the mode of operation (see “PCM Interface Modes”), at least one of these four pins
must be set up as an output by writing to register 4Ch (see Table 57). When not enabled the GPIOs
may be used for other functions on the WM9714L.
PCM INTERFACE MODES
The WM9714L PCM audio interface may be configured in one of four modes:
Four different audio data formats are supported:
All four of these modes are MSB first. They are described below. Refer to the Electrical
Characteristic section for timing information.
Note:
PCMCLK and PCMFS must be synchronized with the BITCLK from the AC’97 interface.
PCM AUDIO DATA FORMATS
•
•
•
•
•
•
•
•
•
•
•
•
GPIO1/PCMCLK: Bit clock
GPIO3/PCMFS: Frame Sync
GPIO4/PCMDAC: Voice DAC data input
GPIO5/PCMADC: Stereo ADC data output
Disabled Mode: The WM9714L disables and tri-states all PCM interface pins. Any
clock input is ignored and ADC/DAC data is not transferred.
Slave Mode: The WM9714L accepts PCMCLK and PCMFS as inputs from an
external source.
Master Mode: The WM9714L generates PCMCLK and PCMFS as outputs.
Partial Master Mode: The WM9714L generates PCMCLK as an output, and
accepts PCMFS as an external input.
DSP mode
Left justified
Right justified
I
2
S
PP, Rev 3.2, October 2008
Pre-Production
26