wm8742 Wolfson Microelectronics plc, wm8742 Datasheet - Page 20

• Manufacturer Part Number: wm8742
• Description: 24-bit 192khz Dac With Advanced Digital Filtering
• Manufacturer: Wolfson Microelectronics plc

WM8742
Figure 11 Initial Setup of Two WM8742 Devices into Control Interface Daisy Chain Mode
Figure 12 Daisy Chain Control Interface Example for Three WM8742 Devices
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To write to a single device in the chain a complete sequence needs to be written to all the devices.
Devices that do not require a register change must also be written to. The user can choose to write
either the same data as the previous write, or write all 1s for the register address and data. All 1s will
result in writing to a non-existent register, address 7Fh, preserving the current register settings.
Figure 12 shows an example of how to access three WM8742 devices (the devices have all
previously been configured in daisy chain mode):
To ensure that only valid data is written to the devices in daisy chain mode, a pull up resistor is used
in SDOUT. When connected to the SDIN pin of the next device in the chain, this results in all ones
being written to the control interface of that device until the correct daisy chain data is written and
latched.
Serial daisy chaining is available only when using 3-wire serial control mode. It is not available in 2-
wire serial control mode or hardware control mode.
Table 9 Control Interface Daisy Chaining Selection
REGISTER ADDRESS
Mode Control 2
08h
R8
BIT
5
SDOUT
LABEL
DEFAULT
0
3 wire Serial Interface Daisy Chaining
0 = No Output
1 = Output on pin 25.
DESCRIPTION
PD, Rev 4.2,August 2009
Production Data
20