WM8991 datasheet(87/174 Pages) WOLFSON

87 / 174 page

Pre-Production

WM8991

PP, May 2008, Rev 3.1

BUTTON CONTROL

The WM8991 GPIO supports button control detection with full status readback for up to seven inputs

(and one IRQ output). All inputs are latched at the IRQ Register, with de-bounce available for normal

operation. De-bouncing may be disabled in order to allow the device to respond to wake-up events

while the processor is disabled and is unable to provide a clock for de-bouncing.

To enable button control and accessory detection, the following register settings are required:

•

ALRCGPIO1 = 1 (only required if using GPIO1)

•

MCLK_SRC = 0 (only required if using GPIO2)

•

AIF_SEL = 0 (only required if using GPIO3, GPIO4 or GPIO5)

•

ALRCGPIO6 = 0 (only required if using GPIO6)

•

LMN3 = 0, LLI3LO = 0 and RLI3LO = 0 (only required if using GPI7)

•

RMN3 = 0, RRI3LO = 0 and LRI3RO = 0 (only required if using GPI8)

•

AIF_TRIS = 0

•

GPIOn_SEL = 0000 for each required GPIO button input

Programmable pull-up and pull-down resistors are available on GPIO1 to GPIO6. These should be

set according to the external circuit configuration. Note that pull-up and pull-down resistors are not

available on the GPI7 and GPI8 input pins. Note that the analogue input paths to GPI7 and GPI8

must be disabled as described above when using these as digital inputs.

In this application, one or more of the GPIO pins may be configured as an Interrupt event if desired.

This is controlled by the GPIOn_IRQ_ENA bits described in Table 46. The GPIO Pin status fields

contained in the IRQ Register (R18) may be read at any time or else in response to an Interrupt

event. See Table 55 for more details of the Interrupt function.

An example configuration of the button control GPIO function is illustrated in Figure 43.

Figure 43 Example of Button Control Using GPIO Pins

Note:

•

The GPIOs 1 to 6 are referenced to DBVDD

•

The GPIs 7 and 8 are referenced to AVDD

WM8991 Datasheet(PDF) 87 Page - Wolfson Microelectronics plc