WM8776 datasheet(22/55 Pages) WOLFSON

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WM8776

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PP Rev 1.91 June 2004

B[15:9] are Control Address Bits

B[8:0] are Control Data Bits

CE is edge sensitive – the data is latched on the rising edge of CE.

2-WIRE SERIAL CONTROL MODE

The WM8776 supports software control via a 2-wire serial bus. Many devices can be

controlled by the same bus, and each device has a unique 7-bit address (this is not the same

as the 7-bit address of each register in the WM8776).

The WM8776 operates as a slave device only. The controller indicates the start of data

transfer with a high to low transition on DI while CL remains high. This indicates that a device

address and data will follow. All devices on the 2-wire bus respond to the start condition and

shift in the next eight bits on DI (7-bit address + Read/Write bit, MSB first). If the device

address received matches the address of the WM8776 and the R/W bit is ‘0’, indicating a

write, then the WM8776 responds by pulling DI low on the next clock pulse (ACK). If the

address is not recognised or the R/W bit is ‘1’, the WM8776 returns to the idle condition and

wait for a new start condition and valid address.

Once the WM8776 has acknowledged a correct address, the controller sends the first byte of

control data (B15 to B8, i.e. the WM8776 register address plus the first bit of register data).

The WM8776 then acknowledges the first data byte by pulling DI low for one clock pulse. The

controller then sends the second byte of control data (B7 to B0, i.e. the remaining 8 bits of

The transfer of data is complete when there is a low to high transition on DI while CL is high.

After receiving a complete address and data sequence the WM8776 returns to the idle state

and waits for another start condition. If a start or stop condition is detected out of sequence

at any point during data transfer (i.e. DI changes while CL is high), the device jumps to the

idle condition.

Figure 20 2-wire Serial Interface

B[15:9] are Control Address Bits

B[8:0] are Control Data Bits

The WM8776 has two possible device addresses, which can be selected using the CE pin.

CE STATE

DEVICE ADDRESS

Low

0011010 (0 x 34h)

High

0011011 (0 x 36h)

Table 11 2-Wire MPU Interface Address Selection

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