WM8728 Datasheet, PDF (17/28 Pages) Wolfson Microelectronics plc – 24-bit, 192kHz Stereo DAC with Volume Control and DSD Support

WM8728
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SOFTWARE CONTROL INTERFACE
The software control interface may be operated using a 2-wire interface compatible or 3-wire (SPI-
compatible) interface.
SELECTION OF CONTROL MODE
The WM8728 may be programmed to operate in hardware or software control modes. This is
achieved by setting the state of the MODE pin.
MODE
INTERFACE FORMAT
0
Hardware Control Mode
1
Software Control Mode
Table 5 Control Interface Mode Selection
3-WIRE (SPI COMPATIBLE) SERIAL CONTROL MODE
In this mode, SDIDEM is used for the program data, SCKDSD is used to clock in the program
data and LATI2S is used to latch in the program data. The 3-wire interface protocol is shown in
Figure 14.
LATI2S
SCKDSD
SDIDEM
B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
Figure 14 3-Wire Serial Interface
Notes:
1. B[15:9] are Control Address Bits
2. B[8:0] are Control Data Bits
3. CSBIWL needs to be low during writes – see Figure 5
2-WIRE SERIAL CONTROL MODE
In 2-wire mode, which is the default, SDIDEM is used for the program data and SCKDSD is used
to clock in the program data see Figure 15.
WM8728 has an address of 001101X (binary) which represents an audio device. The final
address digit is dependent on pin CSBIWL, which should be tied to either DVDD or DGND. This
allows the device to have a choice of two identification header addresses used in the 2 wire
interface word. This feature allows more than one WM8728 device to be present on the interface
bus.
LATI2S should be tied to either DVDD or DGND, as it is unused. This pin if toggled from low to
high and high to low, will cause the device to enter the 3-wire interface mode and cannot be
placed back into 2-wire mode except by toggling the MODE pin, or powering off the device.
SDIDEM
R ADDR
R/W
ACK
DATA B15-8 ACK
DATA B7-0
ACK
SCKDSD
START
Figure 15 2-Wire Serial Interface
STOP
WOLFSON MICROELECTRONICS LTD
PP Rev 1.2 April 2001
17