WM8940 datasheet(59/85 Pages) WOLFSON

59 / 85 page

Pre-Production

WM8940

Pre-Production, Rev 3.0, February 2007

GENERAL PURPOSE INPUT/OUTPUT

In 2-wire mode, the CSB pin is not required and it can be used as a GPIO pin. In 3 wire mode,

the MODE / GPIO can be configured as a GPIO by setting the MODE_GPIO register bit

Whichever pin is used for GPIO, it is controlled from the GPIO control register R8. The GPIOSEL bits

allow the chosen pin to be configured to perform a variety of useful tasks as shown in Table 57.

Note that SLOWCLKEN must be enabled when using the jack detect function.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

5:4

OPCLKDIV

PLL Output clock division ratio

00=divide by 1

01=divide by 2

10=divide by 3

11=divide by 4

GPIOPOL

GPIO Polarity invert

0=Non inverted

1=Inverted

GPIO

control

2:0

GPIOSEL

000

CSB/GPIO pin function select:

000=CSB input

001= Jack insert detect

010=Temp ok

011=Amute active

100=SYSCLK clock o/p

101=PLL lock

110=Reserved

111=Reserved

Table 52 CSB/GPIO Control

CONTROL INTERFACE

SELECTION OF CONTROL MODE AND 2-WIRE MODE ADDRESS

The control interface can operate as either a 3-wire or 2-wire interface. The MODE pin determines

the 2 or 3 wire mode as shown in Table 57.

The WM8940 is controlled by writing to registers through a serial control interface. A control word

consists of 24 bits. The first 7 bits (B23 to B16) are address bits that select which control register is

accessed. The remaining 16 bits (B15 to B0) are register bits, corresponding to the 16 bits in each

control register.

MODE

INTERFACE FORMAT

Low

2 wire

Hi-Z

3 wire

High

3 wire

Table 53 Control Interface Mode Selection

USE OF MODE AS A GPIO PIN IN 3-WIRE MODE

In 3-wire mode, MODE can be used as a GPIO pin. If MODE is being used as a GPIO output, the

partner device doesn’t have to drive MDE - the pin will be pulled-up internally causing 3-wire mode

will be selected. The GPIO function is enabled by setting the MODE_GPIO register bit. The MODE

pin can then be controlled using the GPIO register bits as described in <Table 39> [add as x-

reference].

To use MODE as a GPIO input, MODE must be undriven or driven high at start-up. Specifically

MODE must be high or hi-Z during an initial write to the control interface which sets the

MODE_GPIO register bit. After MODE_GPIO has been set, 3-wire mode selection is overridden

internally and the MODE pin can be used freely as a GPIO input or output.

WM8940 Datasheet(PDF) 59 Page - Wolfson Microelectronics plc

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