wm9704m Wolfson Microelectronics plc, wm9704m Datasheet - Page 12

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

WM9704M
MODEM MODE
WOLFSON MICROELECTRONICS LTD
In Modem mode the modem Tx data is mapped onto the rear DACs. Rear DAC sample rates are set
by the Modem Tx sample rate register 40h, and extended modem capability register 3Ch indicates
Line1 is supported. The following features are supported in Modem Mode:
In order to achieve the above functionality, the following changes to the Rev 2.1 compliant, or quad
mode, defaults are made:
Vendor ID reads back WML4
Headphone channel flagged as ‘not supported’ (bit ID4 in register 00h)
4 channels of DAC and 2 of ADC conversion available, with all recommended Audio and
Modem sample rates supported via the audio sample rate registers 2Ch (front DACs),
40h (rear DACs) and 32h (ADCs in audio mode)
ADC samples are output onto both audio slots 3 & 4 and also line2/1 slots 10 & 5
respectively
Line1 Tx modem data is mapped onto the rear DACs as data and inverted data, so that the
PAIR of rear DACs produce a differential Tx modem data output.
Right audio ADC changes to use line1 sample rate 40h, when input mix selects PHONE
as its IP.
Additional vendor specific mode DLM is available via bit DLM in register 5Ah. Setting this bit
provides support for line2 as well as line1 slots. Rear DACs are mapped onto line1 and line2
Tx modem data slots, and ADC Left and right outputs are mapped both onto normal audio
slots 3 and 4 and also onto the line1 and line2 Rx modem data slots. Modem rate register
40h is used for both DACs and the ADC's use their normal sample rate registers i.e. audio
registers, unless Right channel is selected as PHONE, in which case they too use register
40h.
If DLM bit is set in register 5Ah, then line1 Tx data is mapped onto the rear left DAC, and
Line2 Tx data is mapped onto the rear right DAC. Both rear DACs use the same sample rate
from register 40h (if 42h is written to, 40h will be updated instead)
Left ADC always uses normal ADC audio rate register, except in DLM mode when RPHONE
is selected, when it uses 40h
GPIO capability supporting GPIO (11 to 13) is flagged as supported
Master/slave ID0/1 are supported, with automatic re-mapping of the rear or LFE/center DAC
slot data onto the front DACs when ID 10 or 11 are selected
Headphone/line level output pins 39 and 41 are used to output the rear DAC signals, with
volume controlled from register 04h. Rear mixer PGA is fixed in MUTE condition.
Wolfson 3D stereo enhancement supported
Master volume control register maps to the location dependant on selected ID: (ID 00 or 01
uses master volume at register 02h, ID 10 uses 38h (surround volume) and ID11 uses 36h
(LFE, Center volume) In this case, bits 7 and 15 act as left and right mute.)
Front DAC mute (reg18h) automatically de-muted, when ID is 1x, i.e. used as surround DAC
or LFE/center, when surround or LFE/center master volume is de-muted.
Rear DAC mute (reg70h) automatically de-muted when 04h volume is de-muted
ADC’s always used record level from register 1Ch
Rev 2.1 legacy compliance switch is opened (can be closed using REV2SW bit in register
5Ah)
Rear channel mixer PGA default is now permanently muted, (unlikely that the user wants to
send the analogue mix output onto the Tx modem line output)
Tx modem level at the LNLVL pins still controlled from 04h rather than 46h or 48h (which
would normally be the modem ADC and DAC level control registers)
Rx ADC input levels are still controlled from the normal ADC record level register 1Ch (rather
than 46h or 48h due to the difficulty in re-allocating left and right channel gain controls into
two different registers)
PD Rev 3.2 January 2001
Production Data
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