Sensors

Freescale Semiconductor

39

MMA8451Q

6.6

Single, Double and Directional Tap Detection Registers

For more details of how to configure the tap detection and sample code please refer to Freescale application note, AN4072.

The tap detection registers are referred to as “Pulse”.

0x21: PULSE_CFG Pulse Configuration Register

This register configures the event flag for the tap detection for enabling/disabling the detection of a single and double pulse

on each of the axes.

0x22: PULSE_SRC Pulse Source Register

This register indicates a double or single pulse event has occurred and also which direction. The corresponding axis and event

must be enabled in Register 0x21 for the event to be seen in the source register.

When the EA bit gets set while ELE = 1, all status bits (AxZ, AxY, AxZ, DPE, and PolX, PolY, PolZ) are frozen. Reading the

PULSE_SRC register clears all bits. Reading the source register will clear the interrupt.

0x21 PULSE_CFG Register (Read/Write)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

DPA

ELE

ZDPEFE

ZSPEFE

YDPEFE

YSPEFE

XDPEFE

XSPEFE

Table 43. PULSE_CFG Description

DPA

Double Pulse Abort. Default value: 0.

0: Double Pulse detection is not aborted if the start of a pulse is detected during the time period specified by the PULSE_LTCY register.

1: Setting the DPA bit momentarily suspends the double tap detection if the start of a pulse is detected during the time period specified

by the PULSE_LTCY register and the pulse ends before the end of the time period specified by the PULSE_LTCY register.

ELE

Pulse event flags are latched into the PULSE_SRC register. Reading of the PULSE_SRC register clears the event flag.

Default value: 0.

0: Event flag latch disabled; 1: Event flag latch enabled

ZDPEFE

Event flag enable on double pulse event on Z-axis. Default value: 0.

0: Event detection disabled; 1: Event detection enabled

ZSPEFE

Event flag enable on single pulse event on Z-axis. Default value: 0.

0: Event detection disabled; 1: Event detection enabled

YDPEFE

Event flag enable on double pulse event on Y-axis. Default value: 0.

0: Event detection disabled; 1: Event detection enabled

YSPEFE

Event flag enable on single pulse event on Y-axis. Default value: 0.

0: Event detection disabled; 1: Event detection enabled

XDPEFE

Event flag enable on double pulse event on X-axis. Default value: 0.

0: Event detection disabled; 1: Event detection enabled

XSPEFE

Event flag enable on single pulse event on X-axis. Default value: 0.

0: Event detection disabled; 1: Event detection enabled

0x22 PULSE_SRC Register (Read Only)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

EA

AxZ

AxY

AxX

DPE

PolZ

PolY

PolX

Table 44. PULSE_SRC Description

EA

Event Active Flag. Default value: 0.

(0: No interrupt has been generated; 1: One or more interrupt events have been generated)

AxZ

Z-axis event. Default value: 0.

(0: No interrupt; 1: Z-axis event has occurred)

AxY

Y-axis event. Default value: 0.

(0: No interrupt; 1: Y-axis event has occurred)

AxX

X-axis event. Default value: 0.

(0: No interrupt; 1: X-axis event has occurred)

DPE

Double pulse on first event. Default value: 0.

(0: Single Pulse Event triggered interrupt; 1: Double Pulse Event triggered interrupt)

PolZ

Pulse polarity of Z-axis Event. Default value: 0.

(0: Pulse Event that triggered interrupt was Positive; 1: Pulse Event that triggered interrupt was negative)

PolY

Pulse polarity of Y-axis Event. Default value: 0.

(0: Pulse Event that triggered interrupt was Positive; 1: Pulse Event that triggered interrupt was negative)

PolX

Pulse polarity of X-axis Event. Default value: 0.

(0: Pulse Event that triggered interrupt was Positive; 1: Pulse Event that triggered interrupt was negative)