WM8804 datasheet(17/66 Pages) WOLFSON

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Production Data

WM8804

PD Rev 4.1 September 2007

Multiple consecutive register writes can be performed in 2-wire control mode by setting the CONT bit

high. This method allows the entire register map to be defined in a one continuous write operation.

Figure 12 2-Wire Serial Control Interface Multi-Write

The WM8804 has two possible device addresses, which can be selected using the CSB pin during

hardware reset.

CSB STATE

DEVICE ADDRESS IN

2-WIRE MODE

ADDRESS (X=R/W BIT)

X=0

X= 1

Low

0111010x

0x7A

0x75

High

0111011x

0x76

0x77

Table 11 2-Wire Interface Address Selection

2-WIRE SERIAL CONTROL MODE -REGISTER READ-BACK

The WM8804 allows read-back of certain registers in 2-wire mode. The protocol is similar to that

used to write to the device. The controller will issue the device address followed by a write bit, the

start condition and resend the device address along with a read bit. The WM8804 will acknowledge

this and the WM8804 will become a slave transmitter. The WM8804 will transmit the data from the

indexed register on SDIN MSB first. When the controller receives the data it will not acknowledge

receipt of the data indicating that it will resume master transmitter control of SDIN. The controller will

then issue a stop command completing the read cycle. Figure 13 illustrates the read protocol.

Figure 13 2-Wire Serial Control Interface Read (CONT=0)

2-WIRE SERIAL CONTROL MODE – CONTINUOUS READ-BACK

As in 3-wire mode, there are two methods of reading back data: continuous and non-continuous

read-back. Continuous read-back is selected by setting CONT to 1. In continuous read-back mode,

the device will return the indexed register first followed by consecutive registers in increasing index

order until the controller does not acknowledge the data then issues a stop sequence. This is shown

in Figure 14

Figure 14 2-Wire Serial Interface Continuous Read-Back (CONT=1)

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