WM8946ECSSLASHR datasheet(96/175 Pages) WOLFSON

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WM8946

Production Data

PD, July 2012, Rev 4.3

CONTROL INTERFACE

The WM8946 is controlled by writing to its control registers. Readback is available for all registers.

The Control Interface can operate as either a 2-, 3- or 4-wire interface:



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



3-wire (SPI) mode uses pins CS

¯¯ , SCLK and SDA



4-wire (SPI) mode uses pins CS

¯¯ , SCLK, SDA and SDOUT

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 WM8946 uses 15-bit register addresses and 16-bit data in all Control Interface modes.

SELECTION OF CONTROL INTERFACE MODE

The WM8946 Control Interface can be configured for I2C mode or SPI modes using the

CIFMODE/GPIO3 pin at power-up. The mode selection is as described in Table 63.

CIFMODE/GPIO3

INTERFACE FORMAT

Low

2 wire

High

3- or 4- wire

Table 62 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/GPIO3 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 63. Auto-increment is disabled by default.

In SPI modes, 3-wire or 4-wire operation may be selected using the SPI_4WIRE register bit. In 3-wire

mode, register readback is provided using the bi-directional pin SDA. In 4-wire mode, register

readback is provided using SDOUT. The SDOUT pin may be configured as CMOS or as Open Drain

using the SPI_OD bit. In 3-wire mode the SDA pin may be configured as CMOS or as Open Drain

using the SPI_OD bit. If the open drain option is selected (SPI_OD = 1) then an external pull-up

resistor is required on the SDOUT or SDA output pin.

The Control Interface configuration bits are described in Table 63.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

t(14h)

Control

Interface

SPI_OD

SDOUT pin configuration

(applies to 3-wire and 4-wire mode

only)

0 = SDOUT output is CMOS

1 = SDOUT output is open drain

SPI_4WIRE

SPI control mode select

0 = 3-wire using bidirectional SDA

1 = 4-wire using SDOUT

AUTO_INC

Enables address auto-increment

(applies to 2-wire / I2C mode only)

0 = Disabled

1 = Enabled

Table 63 Control Interface Configuration

WM8946ECS/R Datasheet(PDF) 96 Page - Wolfson Microelectronics plc

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