Specifications

BMA180
Preliminary data sheet
Bosch Sensortec
Rev. 1.0 Page 33 / - proprietary information - 06 March 2009
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Specifications within this document are preliminary and subject to change without notice. Document is not intended for publication.
After setting wake_up to ‘1’, the device goes to the sleep mode and cycle sleep/wake-up/sleep
is started.
The IC wakes-up for a minimum duration which depends on the number of required valid
acceleration data to determine if an interrupt should be generated.
For example, if bw = 0111, low_int = 1 and low_dur = 31d, the IC will need time to acquire a
minimum number of acceleration data: the IC needs low_dur = 31d = 31*5*Tupdate = 64.6ms to
determine if the acceleration is under low_th. Under this example condition, the minimum wake-
up time is 64.6ms. To use smaller wake-up times, low_dur has to be decreased significantly.
To activate wake_up bit in EEPROM, the following procedure is necessary:
1) set register dis_wake_up to “1” (wake-up mode is masked)
2) set image register wake_up to “1”
3) write register wake_up to EEPROM -> dummy write to address 0x54.
4) set register dis_wake_up back to “0” (go to wake-up mode)
To disable wake_up bit in EEPROM, the following procedure is necessary:
5) set register dis_wake_up to “1” (wake-up mode is masked)
6) set image register wake_up to “0”
7) write register wake_up to EEPROM -> dummy write to address 0x54.
8) set register dis_wake_up back to “0” (optional)
7.8.9 wake_up_dur
These bits define the sleep mode duration between each automatic wake-up (timing below is
valid for low-noise mode, in low power mode, sleep mode duration is doubled).
wake_up_dur<1:0> Sleep mode duration
(
ms
)
00
20
01
80
10
320
11
2560
7.8.10 slope_alert
If this bit is at 1, the slope_th_criteria will turn BMA180 in an alert mode. This bit can be masked
by adv_int, the value of this bit is ignored when adv_int = 0 (in other words: if slope_alert is
used, adv_int has to be set to ‘1’).
More explanations to slope alert is given in a separate application note (under preparation).
7.8.11 dis_i2c – disable I²C
This bit could be used to disable the I
2
C mode. Per default, both interfaces are usable (dis_i2c =
“0”), thus automatic switching from SPI to I
2
C when CSB is high is enabled. For disabling I²C,
dis_i2c has to be set to “1”. If SPI-interface is used, it is highly recommended to set dis_i2c to ‘1’
to avoid mal-function.