WM8948ECSSLASHR datasheet(107/189 Pages) WOLFSON

107 / 189 page

Production Data

WM8948

PD, May 2011, Rev 4.1

107

Figure 45 Multiple Register Read from Last Address using Auto-increment

Multiple Write and Multiple Read operations enable the host processor to access sequential blocks of

the data in the WM8948 register map faster than is possible with single register operations. The

auto-increment option is enabled when the AUTO_INC register bit is set. This bit is defined in Table

67. Auto-increment is disabled by default.

3-WIRE (SPI) CONTROL MODE

The 3-wire control interface uses the CS

¯ ¯ , SCLK and SDA pins.

In 3-wire control mode, a control word consists of 32 bits. The first bit is the read/write bit (R/W),

which is followed by 15 address bits (A14 to A0) that determine which control register is accessed.

The remaining 16 bits (B15 to B0) are data bits, corresponding to the 16 bits in each control register.

In 3-wire mode, every rising edge of SCLK clocks in one data bit from the SDA pin. The data is

latched on the 32nd falling edge of SCLK after 32 bits of data have been clocked into the device.

In Write operations (R/W=0), all SDA bits are driven by the controlling device.

In Read operations (R/W=1), the SDA pin is driven by the controlling device to clock in the register

address, after which the WM8948 drives the SDA pin to output the applicable data bits.

Similarly to 2-wire control mode, the WM8948 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 46.

Figure 46 3-Wire Serial Control Interface

4-WIRE (SPI) CONTROL MODE

The 4-wire control interface uses the CS

¯ ¯ , SCLK, SDA and SDOUT pins.

The Data Output pin, SDOUT, can be configured as CMOS or Open Drain, as described in Table 67.

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.

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