Production Data
WM8945
In Read operations (R/W=1), the SDA pin is driven by the controlling device to clock in the register
address, after which the WM8945 drives the SDA pin to output the applicable data bits.
Similarly to 2-wire control mode, the WM8945 can be set to transmit a logic 1 by tri-stating the SDA
pin, rather than pulling it high (SPI_OD = 1). An external pull-up resistor is required to pull the SDA
line high so that the logic 1 can be recognised by the master.
The 3-wire control mode timing is illustrated in Figure 45.
Figure 45 3-Wire Serial Control Interface
4-WIRE (SPI) CONTROL MODE
The 4-wire control interface uses the C¯¯S, SCLK, SDA and SDOUT pins.
The Data Output pin, SDOUT, can be configured as CMOS or Open Drain, as described in Table 66.
In CMOS mode, SDOUT is driven low when not outputting register data bits. In Open Drain mode,
SDOUT is undriven (high impedance) when not outputting register data bits.
In Write operations (R/W=0), this mode is the same as 3-wire mode described above.
In Read operations (R/W=1), the SDATA pin is ignored following receipt of the valid register address.
SDOUT is driven by the WM8945.
The 4-wire control mode timing is illustrated in Figure 46 and Figure 47.
Figure 46 4-Wire Readback (CMOS)
PD, May 2011, Rev 4.1
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