Production Data
WM8805
Figure 12 2-Wire Serial Control Interface Multi-Write
The WM8805 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
0x7A
0x76
X= 1
0x75
0x77
Low
0111010x
0111011x
High
Table 11 2-Wire Interface Address Selection
2-WIRE SERIAL CONTROL MODE -REGISTER READ-BACK
The WM8805 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
register index will then be passed to the WM8805. At this point the controller will issue a repeated
start condition and resend the device address along with a read bit. The WM8805 will acknowledge
this and the WM8805 will become a slave transmitter. The WM8805 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)
PD Rev 4.1 September 07
17
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
