WM8944BECSSLASHR datasheet(91/165 Pages) CIRRUS

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WM8944B

Rev 4.3

CONTROL INTERFACE

The WM8944B is controlled by writing to its control registers. Readback is available for all registers.

The Control Interface can operate as either a 2- or 3-wire interface:



2-wire (I2C) mode uses pins SCLK and SDA



3-wire (SPI) mode uses pins CS

¯¯ , SCLK and SDA

Readback is provided on the bi-directional pin SDA in 2-/3-wire modes.

The device address in 2-wire (I2C) mode is 34h.

The WM8944B uses 15-bit register addresses and 16-bit data in all Control Interface modes.

SELECTION OF CONTROL INTERFACE MODE

The WM8944B Control Interface can be configured for I2C mode or SPI modes using the

CIFMODE/GPIO2 pin at power-up. The mode selection is as described in Table 65.

CIFMODE/GPIO2

INTERFACE FORMAT

Low

2-wire

High

3-wire

Table 64 Control Interface Mode Selection

After the Control Interface Mode has been configured, the MODE_GPIO register bit should be set in

order to latch the selection and to allow GPIO functions to be supported on the CIFMODE/GPIO2 pin.

After the MODE_GPIO register bit has been set, the Control Interface mode selection will remain

latched until a Software Reset or Power On Reset occurs. See “General Purpose Input / Output” for

details.

In 2-wire (I2C) Control Interface mode, Auto-Increment mode may be selected. This enables multiple

write and multiple read operations to be scheduled faster than is possible with single register

operations. The auto-increment option is enabled when the AUTO_INC register bit is set. This bit is

defined in Table 65. Auto-increment is enabled by default.

In 3-wire (SPI) Control Interface mode, register readback is provided using the bi-directional pin SDA.

When the SDA pin is an output, it may be configured as CMOS or as Open Drain using the SPI_OD

bit. An external pull-up resistor is required if using the Open Drain output.

The Control Interface configuration bits are described in Table 65.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R20 (14h)

Control

Interface

SPI_OD

SDA pin output configuration

0 = SDA output is CMOS

1 = SDA output is Open-Drain

AUTO_INC

Enables address auto-increment

(applies to 2-wire / I2C mode only)

0 = Disabled

1 = Enabled

Table 65 Control Interface Configuration

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