WM8912 Datasheet, PDF (86/129 Pages) Wolfson Microelectronics plc – Ultra Low Power DAC with Headphone Driver for Portable Audio Applications

WM8912
Production Data
location. This can be used in order to create placeholders ready for easy adaptation of the sequence.
For example, a sequence could be defined to power-up a mono signal path from DACL to
headphone, with a ‘dummy’ write included to leave space for easy modification to a stereo signal path
configuration. Dummy writes can also be used in order to implement additional time delays between
register writes. Dummy writes are included in the default start-up sequence – see Table 59.
In summary, the Control Register to be written is set by the WSEQ_ADDR field. The data bits that are
written are determined by a combination of WSEQ_DATA_START, WSEQ_DATA_WIDTH and
WSEQ_DATA. This is illustrated below for an example case of writing to the VMID_RES field within
Register R5 (05h).
LSB position = b01
WSEQ_DATA_STARTn = 0001
R5 (05h)
VMID Control 0
b15 b14 b13 b12 b11 b10 b09 b08 b07 b06 b05 b04 b03 b02 b01 b00
VMID_RES
Data Width = 2 bits
WSEQ_DATA_WIDTHn = 0001
WSEQ_DATAn (8 bits) ^{b07 b06 b05 b04 b03 b02 b01 b00}
WSEQ_DATA_WIDTHn = 2 bits.
Therefore, only the Least Significant 2 bits are valid. Bits 02 to 07 are discarded
Figure 53 Control Write Sequencer Example
In this example, the Start Position is bit 01 (WSEQ_DATA_START = 0001b) and the Data width is 2
bits (WSEQ_DATA_WIDTH = 0001b). With these settings, the Control Write Sequencer would
updated the Control Register R5 [2:1] with the contents of WSEQ_DATA [1:0].
DEFAULT SEQUENCES
When the WM8912 is powered up, two Control Write Sequences are available through default
settings in both RAM and ROM memory locations. The purpose of these sequences, and the register
write required to initiate them, is summarised in Table 58. A single register write will initiate the
sequence in both cases.
WSEQ START
INDEX
0 (00h)
WSEQ FINISH
INDEX
22 (16h)
PURPOSE
Start-Up sequence
25 (19h)
39 (27h)
Shutdown sequence
Table 58 Write Sequencer Default Sequences
TO INITIATE
Write 0100h to
Register R111 (6Fh)
Write 0119h to
Register R111 (6Fh)
Note on Shutdown sequence: The instruction at Index Address 25 (19h) shorts the outputs
LINEOUTL and LINEOUTR. If the Line outputs are not in use at the time the sequence is run, then
the sequence could, instead, be started at Index Address 26.
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PD, Rev 4.1, February 2013
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