Specifications

BMA180

Preliminary data sheet

Bosch Sensortec

Rev. 1.0 Page 39 / - proprietary information - 06 March 2009

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

Specifications within this document are preliminary and subject to change without notice. Document is not intended for publication.

• high_int_x: defining if high-g event on x-axis should generate high-g interrupt

• high_int_y: defining if high-g event on y-axis should generate high-g interrupt

• high_int_z: defining if high-g event on z-axis should generate high-g interrupt

• high_filt: evaluation if interrupt generation is done with filtered (high_filt = “1”) or

unfiltered (high_filt = “0”) acceleration signal.

• high_dur: high threshold duration and

• mot_cd_r : motion_counter_down_register are used for debouncing high-g criteria.

Remarks: - The thresholds codes are compared with the 8 MSB bits of acceleration value

(in absolute value), the high threshold level can thus be selected anywhere in

the full scale range.

- The sign of the acceleration, which initiated the interrupt signal, is stored in the

flag bit high_sign_int_*, only if the corresponding enable bit high_int_* is set.

7.9.5.3 High-g interrupt: algorithm

The example in figure 6 for low-g interrupt can easily be transferred to the high-g detection.

When acceleration signal is passing high_th value, high_th_criteria becomes active and counter

mot_cd_r is incremented by 1 N

COUNT

(Ncount = 1 LSB/(5xTupdate) = 1 LSB/2.085ms). Depen-

ding on mot_cd_r register value, the counter could also be reset or count down when

high_th_criteria is false:

mot_cd_r<1:0> High acceleration interrupt counter status when

criteria is false

reset

Count down by 1 N

COUNT

Count down by 2 N

COUNT

Count down by 3 N

COUNT

When the high acceleration interrupt counter value equals high_dur (high_dur <>0), an interrupt

is generated. If high_dur =0, an interrupt is generated as soon as the appropriate criteria is

fulfilled.

The high_th_criteria is set with an OR condition on the three axis to be used as a high-g

detection, thus acceleration signals of minimum 1 axis must be long enough above a certain

thresh-hold.