wm8961 Wolfson Microelectronics plc, wm8961 Datasheet - Page 65

• Manufacturer Part Number: wm8961
• Description: Ultra-low Power Stereo Codec With 1w Stereo Class D Speaker Drivers And Ground Referenced Headphone Drivers
• Manufacturer: Wolfson Microelectronics plc

CONTROL WRITE SEQUENCER
w
WM8961
ADC-DAC LOOPBACK
Setting the LOOPBACK register bit enables digital loopback. When this bit is set the output data from
the ADC audio interface is fed directly into the DAC data input..
Table 48 Loopback Control
The write sequencer allows register write sequences to be stored in an area of memory on the device
and then triggered by another register write. In this way complex sequences of writes can be used to
configure the device without the need for constant intervention by the main processor. This aids pop
and click suppression and simplifies power-on and power-off sequences.
MCLK must be applied to the WM8961 while making use of the write sequencer.
The control write sequencer contains 2 memories. It contains a RAM (locations 0 to 31) and a ROM
(locations 32 to 48). A number of pre-defined sequences are stored within both these areas of
memory. This enables the most popular configurations to be selected via a single command. It also
allows deployment of factory proven ‘patches’ into the field. The pre-defined sequences within the
RAM can be overwritten by the user. This is done by loading new sequences via the control interface
logic shown in Figure 40.
The control interface logic provides connectivity to the control interface and access to the control
registers. In WM8961, a multiplexer has been added to allow switch over, such that the control write
sequencer is connected to the registers instead.
Figure 40 Location of the Control Sequencer in the Control Path
The sequencer allows the controlling processor to initiate a sequence of commands. The delays
between each command in the sequence are controlled on-chip – and are not affected by activities
elsewhere in the system. Once a sequence is initiated, the processor is then free to concentrate on
other parts of the system. A status register is provided to allow the processor to check that one
sequence is complete before starting another.
Although pop and click suppression is the most obvious application, there are other applications. Any
sequence of control writes can be automated, enabling the processor to initiate a thread of
asynchronous control events before performing other tasks or going into a power down mode.
R9
Audio
Interface
REGISTER
ADDRESS
0
BIT
LOOPBACK
LABEL
0
DEFAULT
Digital Loopback Function
0 = No loopback.
1 = Loopback enabled, ADC data output
is fed directly into DAC data input.
DESCRIPTION
PP, August 2009, Rev 3.1
Pre-Production
65