WM8321 datasheet(40/253 Pages) WOLFSON

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WM8321

Production Data

PD, February 2012, Rev 4.0

12 CONTROL INTERFACE

12.1 GENERAL DESCRIPTION

The WM8321 is controlled by writing to its control registers. Readback is available for all registers,

including Chip ID, power management status and GPIO status. The control interface can operate as a

2-wire (I2C) or 4-wire (SPI) control interface. Readback is provided on the bi-directional pin SDA1 in

2-wire (I2C) mode. The WM8321 Control Interface is powered by the DBVDD power domain.

The control interface mode is determined by the logic level on the CIFMODE pin as shown in Table 9.

CIFMODE

INTERFACE FORMAT

Low

2-wire (I2C) mode

High

4-wire (SPI) mode

Table 9 Control Interface Mode Selection

12.2 2-WIRE (I2C) CONTROL MODE

In 2-wire (I2C) mode, the WM8321 is a slave device on the control interface; SCLK1 is a clock input,

while SDA1 is a bi-directional data pin. To allow arbitration of multiple slaves (and/or multiple

masters) on the same interface, the WM8321 transmits logic 1 by tri-stating the SDA1 pin, rather than

pulling it high. An external pull-up resistor is required to pull the SDA1 line high so that the logic 1 can

be recognised by the master.

In order to allow many devices to share a single 2-wire control bus, every device on the bus has a

unique 8-bit device ID (this is not the same as the 16-bit address of each register in the WM8321).

The device ID is determined by the logic level on the CS

¯¯ pin as shown in Table 10. The LSB of the

device ID is the Read/Write bit; this bit is set to logic 1 for “Read” and logic 0 for “Write”.

¯¯

DEVICE ID

Low

0110 100x = 68h(write) / 69h(read)

High

0110 110x = 6Ch(write) / 6Dh(read)

Table 10 Control Interface Device ID Selection

The WM8321 operates as a slave device only. The controller indicates the start of data transfer with a

high to low transition on SDA1 while SCLK1 remains high. This indicates that a device ID, register

address and data will follow. The WM8321 responds to the start condition and shifts in the next eight

bits on SDA1 (8-bit device ID including Read/Write bit, MSB first). If the device ID received matches

the device ID of the WM8321, then the WM8321 responds by pulling SDA1 low on the next clock

pulse (ACK). If the device ID is not recognised or the R/W bit is ‘1’ when operating in write only mode,

the WM8321 returns to the idle condition and waits for a new start condition and valid address.

If the device ID matches the device ID of the WM8321, the data transfer continues as described

below. The controller indicates the end of data transfer with a low to high transition on SDA1 while

SCLK1 remains high. After receiving a complete address and data sequence the WM8321 returns to

the idle state and waits for another start condition. If a start or stop condition is detected out of

sequence at any point during data transfer (i.e. SDA1 changes while SCLK1 is high), the device

returns to the idle condition.

The WM8321 supports the following read and write operations:



Single write



Single read



Multiple write using auto-increment



Multiple read using auto-increment

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