MMA8451 datasheet(15/47 Pages) FREESCALE

15 / 47 page

MMA8452Q

Sensors

Freescale Semiconductor, Inc.

5.9

Interrupt Register Configurations

There are six configurable interrupts in the MMA8452Q: Data Ready, Motion/Freefall, Pulse, Orientation, Transient, and Auto-

SLEEP events. These six interrupt sources can be routed to one of two interrupt pins. The interrupt source must be enabled and

configured. If the event flag is asserted because the event condition is detected, the corresponding interrupt pin, INT1 or INT2,

will assert.

Figure 10. System Interrupt Generation Block Diagram

5.10

Serial I2C Interface

Acceleration data may be accessed through an I2C interface thus making the device particularly suitable for direct interfacing

with a microcontroller. The MMA8452Q features an interrupt signal which indicates when a new set of measured acceleration

data is available thus simplifying data synchronization in the digital system that uses the device. The MMA8452Q may also be

configured to generate other interrupt signals accordingly to the programmable embedded functions of the device for Motion,

Freefall, Transient, Orientation, and Pulse.

The registers embedded inside the MMA8452Q are accessed through the I2C serial interface (Table 9). To enable the I2C

interface, VDDIO line must be tied high (i.e., to the interface supply voltage). If VDD is not present and VDDIO is present, the

MMA8452Q is in off mode and communications on the I2C interface are ignored. The I2C interface may be used for

communications between other I2C devices and the MMA8452Q does not affect the I2C bus.

There are two signals associated with the I2C bus; the Serial Clock Line (SCL) and the Serial Data line (SDA). The latter is a

bidirectional line used for sending and receiving the data to/from the interface. External pullup resistors connected to VDDIO are

expected for SDA and SCL. When the bus is free both the lines are high. The I2C interface is compliant with fast mode (400 kHz),

and Normal mode (100 kHz) I2C standards (Table 5).

Table 9. Serial Interface Pin Description

Pin Name

Pin Description

SCL

I2C Serial Clock

SDA

I2C Serial Data

SA0

I2C least significant bit of the device address

INTERRUPT

CONTROLLER

Data Ready

Motion/Freefall

Pulse

Orientation

Transient

Auto-SLEEP

INT ENABLE

INT CFG

INT1

INT2

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