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
Hardware Control Mode
Software Control Mode
0
1
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
B15
B14
B13
B12
B11
B10
B9
B8
B7
B6
B5
B4
B3
B2
B1
B0
SDIDEM
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.
ACK
ACK
ACK
DATA B15-8
R ADDR
R/W
DATA B7-0
SDIDEM
SCKDSD
START
STOP
Figure 15 2-Wire Serial Interface
WOLFSON MICROELECTRONICS LTD
PP Rev 1.2 April 2001
17
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
