WM8993 datasheet(143/229 Pages) WOLFSON

143 / 229 page

Production Data

WM8993

PD, November 2010, Rev 4.0

143

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 both of the Headphone start-up sequences -

see Table 95 and Table 96.

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 ADCL_DAC_SVOL field

within Register R13 (0Dh).

In this example, the Start Position is bit 09 (WSEQ_DATA_START = 1001b) and the Data width is 4

bits (WSEQ_DATA_WIDTH = 0011b). With these settings, the Control Write Sequencer would

update the Control Register R13 [12:9] with the contents of WSEQ_DATA [3:0].

Figure 68 Control Write Sequencer Example

DEFAULT SEQUENCES

When the WM8993 is powered up, a number of Control Write Sequences are available through

default settings in both RAM and ROM memory locations. The pre-programmed default settings

include Start-Up and Shut-Down sequences for each of the output drivers. Note that the default

sequences do not include audio signal path or gain setting configuration; this must be implemented

prior to scheduling any of the default Start-Up sequences.

Index addresses 0 to 31 may be programmed to users’ own settings at any time, as described in

“Programming a Sequence”. Users’ own settings remain in memory regardless of WSEQ_ENA, and

are not affected by software resets (i.e. writing to Register R0). However, any non-default sequences

are lost when the device is powered down.

WM8993 Datasheet(PDF) 143 Page - Wolfson Microelectronics plc