BMA150 datasheet(21/56 Pages) BOSCH

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Data sheet

BMA150

Triaxial, digital acceleration sensor

Bosch Sensortec

Rev. 1.6

Page 21

30 October 2008

as copying and passing on to third parties. BOSCH and the symbol are registered trademarks of Robert Bosch GmbH, Germany.

Note: Specifications within this document are subject to change without notice.

3.3.4 Selftest_0

The self-test command (address 0Ah, bit 2) uses electrostatic forces to move the MEMS

common electrode. The result from selftest can be verified by reading st_result (section 3.4.1).

During selftest procedurno external change of the acceleration should be generated.

3.3.5 Selftest_1

This self test bit (address 0Ah, bit3) does not generate any electrostatic force in the MEMS

element but is used to verify the interrupt function is working correctly and that microprocessor

is able to react to the interrupts.

0g acceleration is emulated at ADC input and the user can detect the whole logic path for

interrupt, including the PCB path integrity. The LG_thres register must be set to about 0.4g

while LG_dur = 0 to generate a low-g interrupt

3.3.6 Soft_reset

BMA150 is reset each time this bit (address 0Ah, bit 1) is written to 1. The effect is identical to

power-on reset. Control, status and image registers are reset to values stored in the EEPROM.

After soft_reset or power-on reset BMA150 comes up in normal mode or wake-up mode. It is

not possible to boot BMA150 to sleep mode.

No serial transaction should occur within 10us after soft_reset command.

The soft_reset procedure may overwrite the SPI4 setting (section 3.1.1). Thus the correct

interface configuration may have to be updated.

3.3.7 Sleep

This bit (address 0Ah, bit 0) turns the sensor IC in sleep mode. Control and image registers are

not cleared.

When BMA150 is in sleep mode no operation can be performed but wake-up the sensor IC by

setting sleep=0 or soft_reset. As a consequence all write and read operations are forbidden

when the sensor IC is in sleep mode except command used to wake up the device or soft_reset

command. After sleep mode removal, it takes 1ms to obtain stable acceleration values (>99%

data integrity). User must wait for 10ms before first EEPROM write. For the same reason,

BMA150 must not be turned in sleep mode when any update_image, self_test or EEPROM

write procedure is on going.

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