AN2989

Startup sequence

Doc ID 15761 Rev 1

7/28

2

Startup sequence

Once the device is powered up it automatically downloads the calibration coefficients from

the embedded Flash to the internal registers. When the boot procedure is complete (after

approximately 5 milliseconds), the device automatically enters power-down mode.

To turn on the device and gather acceleration data, it is necessary to select one of the

operating modes through the CTRL_REG1 register, and to enable at least one of the axes.

The following general-purpose sequences can be used to configure the device:

1.

write CTRL_REG1

2.

write CTRL_REG2

3.

write CTRL_REG3

4.

write CTRL_REG4

5.

write Reference

6.

write INT1_THS

7.

write INT1_DUR

8.

write INT2_THS

9.

write INT2_DUR

10. read HP_FILTER_RESET (if filter is enabled)

11. write INT1_CFG

12. write INT2_CFG

13. write CTRL_REG5

Register values can be changed at any time, with the device in any operating mode.

Modifications take effect immediately.

Note that in case of changes in full scale, ODR or enabling/disabling of self-test, the output

of the device requires 3 to 8 samples to settle (see Table 11). In cases where the HP filter

cut-off frequency is changed, the filter can be reset by reading HP_FILTER_RESET register.