WM8581 datasheet(23/100 Pages) WOLFSON

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Production Data

WM8581

PD Rev 4.0 April 2007

2-WIRE SERIAL CONTROL MODE WITH READ-BACK

The WM8581 supports software control via a 2-wire read/write serial bus. Many devices can be

controlled by the same bus, and each device has a unique 7-bit address (see Table 10).

The controller indicates the start of data transfer with a high to low transition on SDIN while SCLK

remains high. This indicates that a device address, DEVA(7:1), and data REG(6:0) will follow. All

devices on the 2-wire bus respond to the start condition and shift in the next eight bits on SDIN (7-bit

address + Read/Write bit, MSB first). If the device address received matches the address of the

WM8581, the WM8581 responds by pulling SDIN low on the next clock pulse (ACK). If the address is

not recognised, the WM8581 returns to the idle condition and wait for a new start condition and valid

address.

Once the WM8581 has acknowledged a correct address, the controller sends the first byte of control

data (REGA(6:0), i.e. the WM8581 register address plus the first bit of register data). The WM8581

then acknowledges the first data byte by pulling SDIN low for one clock pulse. The controller then

sends the second byte of control data (DIN(7:0), i.e. the remaining 8 bits of register data), and the

WM8581 acknowledges by driving SDIN low.

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

After receiving a complete address and data sequence the WM8581 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. SDIN changes while SCLK is high), the device returns to the idle condition.

Figure 9 2-Wire Serial Control Interface

The WM8581 has two possible device addresses, which can be selected using the CSB pin.

CSB STATE

DEVICE ADDRESS IN 2-

WIRE MODE

ADDRESS (X=R/W BIT)

X=0

X= 1

Low or Unconnected

0011010x

0x34

0x35

High

0011011x

0x36

0x37

Table 10 2-Wire MPU Interface Address Selection

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