WM8581 datasheet(20/94 Pages) WOLFSON

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WM8581

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PP Rev 1.0 March 2006

2-WIRE SERIAL CONTROL MODE WITH READ-BACK

The WM8581 supports software control via a 2-wire (2-wire write, 3-wire read) 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 and data 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 (B15 to B8, 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 (B7 to B0, i.e. the remaining 8 bits of register data), and the

WM8581 acknowledges again by pulling 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 jumps 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

Low or Unconnected

0011010

High

0011011

Table 10 2-Wire MPU Interface Address Selection

SDIN

SCLK

address

ack

B15-B8

ack

B7-B0

ack

device address

[wr=0]

STOP

START

out

address and

1st data bit

remaining data

bits

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