wm8918 Wolfson Microelectronics plc, wm8918 Datasheet - Page 117

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

Production Data
w
Having set the Index as described above, Register R109 must be written to (containing the Control
Register Address, the Start Bit Position and the Field Width applicable to this step of the sequence).
Also, Register R110 must be written to (containing the Register Data, the End of Sequence flag and
the Delay time required after this step is executed). After writing to these two registers, the next step
in the sequence may be programmed by updating WSEQ_WRITE_INDEX and repeating the
procedure.
WSEQ_ADDR is an 8-bit field containing the Control Register Address in which the data should be
written.
WSEQ_DATA_START is a 4-bit field which identifies the LSB position within the selected Control
Register to which the data should be written. Setting WSEQ_DATA_START = 0100 will cause 1-bit
data to be written to bit 4. With this setting, 4-bit data would be written to bits 7:4 and so on.
WSEQ_DATA_WIDTH is a 3-bit field which identifies the width of the data block to be written. This
enables selected portions of a Control Register to be updated without any concern for other bits
within the same register, eliminating the need for read-modify-write procedures. Values of 0 to 7
correspond to data widths of 1 to 8 respectively. For example, setting WSEQ_DATA_WIDTH = 010
will cause a 3-bit data block to be written. Note that the maximum value of this field corresponds to
an 8-bit data block; writing to register fields greater than 8 bits wide must be performed using two
separate operations of the Control Write Sequencer.
WSEQ_DATA is an 8-bit field which contains the data to be written to the selected Control Register.
The WSEQ_DATA_WIDTH field determines how many of these bits are written to the selected
register; the most significant bits (above the number indicated by WSEQ_DATA_WIDTH) are
ignored.
WSEQ_DELAY is a 4-bit field which controls the waiting time between the current step and the next
step in the sequence. The total delay time per step (including execution) is given by:
This gives a useful range of execution/delay times from 562μs up to 2.048s per step.
WSEQ_EOS is a 1-bit field which indicates the End of Sequence. If this bit is set, then the Control
Write Sequencer will automatically stop after this step has been executed.
R108 (6Ch)
Write
Sequencer
0
R109 (6Dh)
Write
Sequencer
1
REGISTER
ADDRESS
T = k × (2
where k = 62.5μs (under recommended operating conditions)
14:12
11:8
BIT
4:0
7:0
WSEQ_DELAY
WSEQ_WRITE
WSEQ_DATA_
WSEQ_DATA_
WSEQ_ADDR
_INDEX [4:0]
WIDTH [2:0]
START [3:0]
LABEL
+ 8)
[7:0]
0000_0000
DEFAULT
0_0000
0000
000
Sequence Write Index. This is the
memory location to which any updates
to R109 and R110 will be copied.
0 to 31 = RAM addresses
Width of the data block written in this
sequence step.
000 = 1 bit
001 = 2 bits
010 = 3 bits
011 = 4 bits
100 = 5 bits
101 = 6 bits
110 = 7 bits
111 = 8 bits
Bit position of the LSB of the data
block written in this sequence step.
0000 = Bit 0
…
1111 = Bit 15
Control Register Address to be written
to in this sequence step.
PD, Rev 4.0, September 2010
DESCRIPTION
WM8918
117