WM8581SEFT Wolfson Microelectronics Ltd., WM8581SEFT Datasheet - Page 20

• Manufacturer Part Number: WM8581SEFT
• Description: Multichannel Codec with S/pdif Transceiver
• Manufacturer: Wolfson Microelectronics Ltd.

WM8581
w
SCLK
SDIN
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.
Table 10 2-Wire MPU Interface Address Selection
Low or Unconnected
START
CSB STATE
High
address
device address
[wr=0]
in
DEVICE ADDRESS IN 2-
wr
WIRE MODE
0011010
0011011
ack
out
address and
1st data bit
B15-B8
register
in
ack
out
remaining data
B7-B0
bits
in
PP Rev 1.0 March 2006
Product Preview
ack
out
STOP
20