Specifications

BMA180
Preliminary data sheet
Bosch Sensortec
Rev. 1.0 Page 42 / - proprietary information - 06 March 2009
© Bosch Sensortec GmbH reserves all rights even in the event of industrial property rights. We reserve all rights of disposal such
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.
7.9.6.3 slope interrupt: algorithm
An example of slope detection (here bw = 0111b, slope_dur = 01b, slope_int = 1) is shown
below. At a certain time, a high slope is detected and INT is set to “1” (high slope has to stay for
3 consecutive data points, here until time t0). If slope is decreased, after a certain time low
slope is detected (again after 3 consecutive data points) and INT is reset at time t1 to “0”.
417us for 1.2kHz bandwidth
Acceleration
1
st
2
n
d
3
rd
low slope detected
at this time
high slope detected
at this time
1
st
2
nd
3
rd
IF slope_int=1, INT=1 from t0 to t1
Time
IF slope_alert=1, alert mode is set from t0
t0 t1
Figure 8: acceleration slope detection, example with slope_dur = 01b, 3 consecutive
slope criteria must be detected.
slope_dur is used to filter the slope detection and also to determine minimum interrupt duration
because the reset condition is also filtered. The minimum interrupt duration is
slope_dur*n*Tupdate.
slope_dur<1:0> Number of required consecutiv conditions
to set or reset the
slo
p
e th criteria
00
1
01
3
10
5
11
7
slope_th_criteria can be used to generate a slope interrupt or to put BMA180 in alert mode; this
is selected by slope_int and slope_alert settings. These 2 modes can not be turned ON
simultaneously.
The sign of the last slope, which has initiated the interrupt or alert signal, is stored in the flag bit
slope_sign_int_*, only if the corresponding enable bit slope_int_* is set. slope_sign_int_* is 2’s
complement coded (0 = positive slope; 1 = negative one).