WM8591
Product Preview
Figure 17 DSP/PCM Mode Audio Interface (mode A, LRP=0, Slave)
Figure 18 DSP/PCM Mode Audio Interface (mode B, LRP=0, Slave)
CONTROL INTERFACE OPERATION
The WM8591 is controlled by writing to registers through a serial control interface. A control word
consists of 16 bits. The first 7 bits (B15 to B9) are address bits that select which control register is
accessed. The remaining 9 bits (B8 to B0) are data bits, corresponding to the 9 bits in each control
register. The control interface operates as a 2-wire MPU interface.
2-WIRE SERIAL CONTROL
The WM8591 supports software control via a 2-wire serial bus. 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 7-bit address
of each register in the WM8591).
The controller indicates the start of data transfer with a high to low transition on DI while CL 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 DI (7-bit address + Read/Write bit, MSB first).
If the device address received matches the address of the WM8591 and the R/W bit is ‘0’, indicating
a write, then the WM8591 responds by pulling DI low on the next clock pulse (ACK). If the address is
not recognised or the R/W bit is ‘1’, the WM8591 returns to the idle condition and wait for a new start
condition and valid address.
Once the WM8591 has acknowledged a correct address, the controller sends the first byte of control
data (B15 to B8, i.e. the WM8591 register address plus the first bit of register data). The WM8591
then acknowledges the first data byte by pulling DI low for one clock pulse. The controller then sends
the second byte of control data (B7 to B0, i.e. the remaining 8 bits of register data), and the WM8591
acknowledges again by pulling DI low.
PP Rev 1.0 May 2005
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
