HI Henry Wu,
Answering to your first question regarding the difference between FXL and MMA in our accelerometers naming, there are no functionality changes, is more related to the part number schemes, basically all of our “older” part number accelerometers starts with MMA and the newest accelerometers part numbers starts with “FXL”.
For your second question regarding the Roll Over Function, according to my understanding a car roll over is basically searching for a quick change in the angulation of the vehicle and it involves forces from 2g to 8g, please correct me if I’m wrong.
Unfortunately none of the Freescale accelerometers have embedded the function of rollover detection, so you would need to calculate it by yourself, however, you can probably use the detection of change of tilt angle exceeding a threshold of the embedded Vector-Magnitude function on the FXLS8471Q as described in the application note AN4692: www.freescale.com/files/sensors/doc/app_note/AN4692.pdf
This Application note comes with an associated software that you can download from the following link: www.freescale.com/files/sensors/doc/app_note/AN4692SW.zip
I hope this helps.
Have a great day,
Jose Reyes
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