WM8778 datasheet(21/50 Pages) WOLFSON

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WM8778

PP Rev 1.7 June 2004

The MSB of the left channel ADC data is output on DOUT and changes on the same falling edge of

ADCBCLK as the low to high ADCLRC transition and may be sampled on the rising edge of

ADCBCLK. The right channel ADC data is contiguous with the left channel data (Figure 18).

ADCLRC

ADCBCLK

DOUT

Word Length (WL)

1/fs

LEFT CHANNEL

n-1

LSB

MSB

n-1

RIGHT CHANNEL

NO VALID DATA

Figure 18 DSP Late Mode Timing Diagram – ADC Data Output

In both early and late DSP modes, the left channel is always sent first, followed immediately by the

right channel. No DACBCLK edges are allowed between the data words.

CONTROL INTERFACE OPERATION

The WM8778 is controlled by writing to registers through a serial control interface. A control word

consists of 16 bits. The first 7 bits (B15 to B9) are address bits that select which control register is

accessed. The remaining 9 bits (B8 to B0) are data bits, corresponding to the 9 bits in each control

selects the interface format, as shown in Table 10.

MODE

CONTROL MODE

2 wire software

Z / midrail

Hardware

3 wire software

Table 10 Control Interface Selection via MODE Pin

The control interface is 5V tolerant, meaning that the control interface input signals CE, CL and DI as

well as MODE may have an input high level of 5V while DVDD is 3V. Input thresholds are determined

by DVDD.

3-WIRE (SPI COMPATIBLE) SERIAL CONTROL MODE

In 3-wire mode, every rising edge of CL clocks in one data bit from the DI pin. A rising edge on CE

latches in a complete control word consisting of the last 16 bits. The 3-wire interface protocol is

shown in Figure 19.

Figure 19 3-wire SPI Compatible Interface

B15

B14

B13

B12

B11

B10

control register address

control register data bits

latch

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