Specifications

BMA180
Preliminary data sheet
Bosch Sensortec
Rev. 1.0 Page 55 / - 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.
7.12.8 Status bits for acceleration or slope sign
These latched status bits can be used by microprocessor to know the sign of the acceleration or
the slope which has initiated an interrupt or alert signal (‘0’ for a positive sign, ‘1’ for a negative
one).
If the INT pad shall be asserted, sign bits are updated. The bits corresponding to the disabled
axes are set to ‘0’, the other ones are set to the corresponding sign. If the whole interrupt has
been disabled, all the appropriate sign bitsa re set to ‘0’. If just one axis is disabled/enabled, the
appropriate sign bit is not touched; it is updated as soon as there is a generated interrupt.
Latched status registers can only be reset by power-on reset or soft-reset.
7.12.9 ee_write
This bit is set to ‘1’ if EEPROM writing is in progress. Any writing transaction sent if ee_write =
‘1’ is ignored.
7.13 Data registers
7.13.1 temp
A thermometer is embedded in BMA180, temperature resolution is 0.5 K/LSB
TEMP
. Code 80h
stands for lowest temperature which is centered around -40°C and typical code for 25°C is
00000010 in 2’s complement. Offset and gain are trimmable like the acceleration axes, thus
temperature offset could be adjusted to achieve a range between -40°C and 87.5°C by
changing the offset_t register (typical value 88d)
7.13.2 acc_x, acc_y, acc_z
Acceleration values are stored in these registers to be read out through serial interface. The
description of the digital signals acc_x, acc_y and acc_z is “2’s complement”, based on 14 bits.
The 2 LSB are fixed to 0 if readout_12bit is set to ‘1’.
From negative to positive accelerations, the following sequence for the ±2g measurement range
can be observed (all other g-ranges correspondingly):
-2.00000 g : 10 0000 0000 0000
-1.99975 g : 10 0000 0000 0001
...
-0.00025 g : 11 1111 1111 1111
0.00000 g : 00 0000 0000 0000
+0.00025g : 00 0000 0000 0001
...
+1.99950g : 01 1111 1111 1110
+1.99975g : 01 1111 1111 1111
Data is periodically updated with values from the digital filter output. LSB acceleration bytes
must be read first. After an acceleration LSB byte read access, the corresponding MSB byte