WM9705_06 WOLFSON [Wolfson Microelectronics plc], WM9705_06 Datasheet - Page 21

• Manufacturer Part Number: WM9705_06
• Manufacturer: WOLFSON [Wolfson Microelectronics plc]

WM9705
Table 2 DAC and SPDIF Slot Mapping Defaults
PRIMARY/SECONDARY ID SUPPORT
HEADPHONE DRIVE AND HEADSET AUTODETECT
w
‘lo’ (rev2.2 compliant)
‘lo’ (rev2.2 compliant)
‘hi’ (WM proprietary)
‘hi’ (WM proprietary)
SPEN STATE AT
START-UP
‘hi’ = ID = 0 = primary
‘lo’ = ID = 1 = secondary
‘hi’ = ID = 0 = primary
‘lo’ = ID = 1 = secondary
However, an exception to the rev2.2 mapping table is made when SPDIF operation is enabled
using the SPEN hardware enable pin (being held high at start-up): in this case SPDIF data is
immediately output from the DAC primary slots 3 and 4. This allows for driver-less SPDIF
operation, where the SPDIF or I
channels. Channel status and control bits output along with the SPDIF data are as set in the
SPDIF control register 3Ah. If required SPDIF data channel slot mapping may be then changed
by setting SPSA bits as required. See tables 18, 19 and 20 for further details.
A mode is provided where the output from the ADC is sent out as the SPDIF or I
above, rather than the data sent to the DACs over the AC link. This mode is enabled by setting bit
ADCO in register 5Ch. ADC data continues to be sent via the AC link to the controller as normal.
WM9705 supports SPDIF and I
in register 3Ah any value other than the default 48ks/s rate will result in a fail to write, with the
48ks/s value being returned on subsequent reads of these values.
WM9705 supports operation as either a primary or a secondary codec. Configuration of the
device as either a primary or as a secondary, is selected by tying the CID0 pin 45 on the package.
Fundamentally, a device identified as a primary (ID = 0, CID0 = ‘hi’) produces BITCLK as an
output, whereas a secondary (any other ID) must be provided with BITCLK as an input. This has
the obvious implication that if the primary device on an AC link is disabled, the secondary devices
cannot function. The AC’97 Revision 2.2 specification defines that the CID0 pin has inverting
sense, and are provided with internal weak pull ups. Therefore, if no connections are made to the
CID0 pin, then the pin pull hi and an ID = 0 is selected, i.e. primary. External connect to ground
(with pull-down from 0 to 10k Ω ) will select codec ID = ‘1’.
Table 3 Codec ID Selection
Headphone drive capability is provided on the HPOUT output pins 39 and 41 (called AUXOUT in
AC’97 rev2.2 specification) and also on the MONOOUT output pin 37.
Headphones of impedance typically from 16 Ω upwards may be connected to these pins. AC
coupling with an appropriately sized capacitor is recommended for removal of the mid-rail DC
pedestal present on these outputs. AC’97 rev2.2 specification recommends 32 Ω headphones; if a
headphone is connected for use as a headset, where the stereo ear-pieces are driven in parallel,
then each capsule must be of minimum 32 Ω impedance.
In many applications it is desirable to be able to connect either a stereo headphone to the
headphone output pins, or a mono headset, comprising ear-piece(s) and a microphone. The
microphone signal is sent via the tip connected wire of the typical 3-wire jack. In this event it is
desirable to be able to auto-detect the connection of either the headphone or the headset (with
microphone). The main characteristic of the headset and microphone compared to the
headphone is that the microphone impedance is typically much higher than the headphone
capsule (assuming a typical moving coil headphone). Because of this it is possible to connect a
weak pull-up to the tip connection of the headphone jack.
CODEC ID (PIN 45 STRAPPING)
NC or pull-up
PIN 45 CID0
Ground
SELECTED
ID
0
1
2
S data only at the default 48ks/s frame rate. Writing to SPSR bits
2
S output is simply the data contained in the main audio DAC
Slots 7 and 8 – surround
Slots 3 and 4 - front channels
Slots 7 and 8 – surround
Slots 3 and 4 - front channels
PRIMARY OR
SECONDARY
Secondary
Primary
AUDIO DAC SLOT
DEFAULT
BITCLK
Output
Input
Slots 7 and 8
Slots 6 and 9
Slots 3 and 4
Slots 3 and 4
DATASLOT DEFAULT
PD Rev 4.4 August 2006
SPDIF OR I
Production Data
2
S data as
2
S
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