WM8961
Pre-Production
CONTROL INTERFACE
The WM8961 is controlled by writing to registers through a 2-wire serial control interface. A control
word consists of 24 bits. The first 8 bits (B23 to B16) are address bits that select which control register
is accessed. The remaining 16 bits (B15 to B0) are data bits, corresponding to the 16 bits in each
control register. Many devices can be controlled by the same bus, and each device has a unique 7-bit
address (this is not the same as the 8-bit address of each register in the WM8961). The default device
address is 1001010x (0x94h).
The WM8961 operates as a slave device only. 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 WM8961, then the WM8961 responds by pulling SDIN low on the next clock pulse
(ACK). If the address is not recognised or the R/W bit is ‘1’ when operating in write only mode, the
WM8961 returns to the idle condition and wait for a new start condition and valid address.
By default, the WM8961 control interface requires an MCLK to be present before register writes are
supported. To access the control interface without an MCLK, the user must set R8 (08h) Clocking2 bit
5 (CLK_SYS_ENA) =0. MCLK is not required to write to CLK_SYS_ENA.
Without MCLK, and with CLK_SYS_ENA=0, all registers can be updated and will maintain their
settings, however any changes to functionality of the write sequencer, headphone PGAs, and
headphone output stage will not take effect until MCLK is present. Enabling MCLK after the register
writes to enable the headphone PGA and headphone output stage may produce audible pops and
clicks, hence is not recommended.
The WM8961 supports several kinds of read and write operations, which are:
•
•
•
•
Single write
Single read
Multiple write using auto-increment
Multiple read using auto-increment
Auto-increment is enabled by default and can be disabled using the AUTO_INC bit as detailed in
Table 3.
These modes are shown in the section below. Terminology used in the following figures is as follows:
TERMINOLOGY
DESCRIPTION
Start Condition
Repeated start
Acknowledge
Stop Condition
S
Sr
A
P
RW
ReadNotWrite
0 = Write
1 = Read
Table 2 Terminology
PP, August 2009, Rev 3.1
w
20
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
