wm8918 Wolfson Microelectronics plc, wm8918 Datasheet - Page 81

• Manufacturer Part Number: wm8918
• Description: Ultra Low Power Dac For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

Production Data
DIGITAL AUDIO INTERFACE
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Table 49 DC Servo Active Modes
DC SERVO READBACK
The current DC offset value for each Line and Headphone output channel can be read in two’s
complement format from the DCS_DAC_WR_VAL_n [7:0] bit fields in Registers R73, R74, R75 and
R76. Note that these values may form the basis of settings that are subsequently used by the DC
Servo in DAC Write mode.
The digital audio interface is used for inputting DAC data to the WM8918 and outputting Digital
Microphone data from it. The digital audio interface uses four pins:
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•
•
•
The clock signals BCLK and LRCLK can be outputs when the WM8918 operates as a master, or
inputs when it is a slave (see “Master and Slave Mode Operation”, below).
Four different audio data formats are supported:
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•
•
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R72 (48h)
DC Servo 5
R69 (45h)
DC Servo 2
REGISTER
ADDRESS
AIFTXDAT: Digital Microphone data output
AIFRXDAT: DAC data input
LRCLK: Left/Right data alignment clock
BCLK: Bit clock, for synchronisation
Left justified
Right justified
I2S
DSP mode
11:8
BIT
6:0
3:0
DCS_TIMER_PE
DCS_TIMER_PE
DCS_SERIES_N
RIOD_23 [3:0]
RIOD_01 [3:0]
O_01 [6:0]
LABEL
DEFAULT
010 1010
1010
1010
Number of DC Servo updates to
perform in a series event for
HPOUTL/HPOUTR.
0 = 1 updates
1 = 2 updates
...
127 = 128 updates
Time between periodic updates for
LINEOUTL/LINEOUTR. Time is
calculated as 0.256s x (2^PERIOD)
0000 = Off
0001 = 0.52s
1010 = 266s (4min 26s)
1111 = 8519s (2hr 22s)
Time between periodic updates for
HPOUTL/HPOUTR. Time is calculated
as 0.256s x (2^PERIOD)
0000 = Off
0001 = 0.52s
1010 = 266s (4min 26s)
1111 = 8519s (2hr 22s)
PD, Rev 4.0, September 2010
DESCRIPTION
WM8918
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