WM8912 datasheet(86/128 Pages) WOLFSON

86 / 128 page

WM8912

Production Data

PD, Rev 4.0, September 2010

Note that a ‘Dummy’ write can be inserted into a control sequence by commanding the sequencer to

write a value of 0 to bit 0 of Register R255 (FFh). This is effectively a write to a non-existent register

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

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

WSEQ FINISH

INDEX

PURPOSE

TO INITIATE

0 (00h)

22 (16h)

Start-Up sequence

Write 0100h to

25 (19h)

39 (27h)

Shutdown sequence

Write 0119h to

Table 58 Write Sequencer Default Sequences

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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