LSM6DST datasheet(58/180 Pages) STMICROELECTRONICS

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Functionality

LSM6DST

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DocID033525 Rev 2

The FIFO buffer can be configured according to six different modes:



Bypass mode



FIFO mode



Continuous mode



Continuous-to-FIFO mode



Bypass-to-continuous mode



Bypass-to-FIFO mode

Each mode is selected by the FIFO_MODE_[2:0] bits in the FIFO_CTRL4 (0Ah) register.

6.6.1

Bypass mode

In Bypass mode (FIFO_CTRL4 (0Ah)(FIFO_MODE_[2:0] = 000), the FIFO is not operational

and it remains empty. Bypass mode is also used to reset the FIFO when in FIFO mode.

6.6.2

FIFO mode

In FIFO mode (FIFO_CTRL4 (0Ah)(FIFO_MODE_[2:0] = 001) data from the output

channels are stored in the FIFO until it is full.

To reset FIFO content, Bypass mode should be selected by writing FIFO_CTRL4

(0Ah)(FIFO_MODE_[2:0]) to '000'. After this reset command, it is possible to restart FIFO

mode by writing FIFO_CTRL4 (0Ah)(FIFO_MODE_[2:0]) to '001'.

The FIFO buffer memorizes up to 9 kbytes of data (with compression enabled) but the depth

of the FIFO can be resized by setting the WTM [8:0] bits in FIFO_CTRL1 (07h) and

FIFO_CTRL2 (08h). If the STOP_ON_WTM bit in FIFO_CTRL2 (08h) is set to '1', FIFO

depth is limited up to the WTM [8:0] bits in FIFO_CTRL1 (07h) and FIFO_CTRL2 (08h).

6.6.3

Continuous mode

Continuous mode (FIFO_CTRL4 (0Ah)(FIFO_MODE_[2:0] = 110) provides a continuous

FIFO update: as new data arrives, the older data is discarded.

A FIFO threshold flag FIFO_STATUS2 (3Bh)(FIFO_WTM_IA) is asserted when the number

of unread samples in FIFO is greater than or equal to FIFO_CTRL1 (07h) and FIFO_CTRL2

(08h)(WTM [8:0]).

It is possible to route the FIFO_WTM_IA flag to the INT1 pin by writing in register

INT1_CTRL (0Dh)(INT1_FIFO_TH) = '1' or to the INT2 pin by writing in register INT2_CTRL

(0Eh)(INT2_FIFO_TH) = '1'.

A full-flag interrupt can be enabled, INT1_CTRL (0Dh)(INT1_FIFO_FULL) = '1' or

INT2_CTRL (0Eh)(INT2_FIFO_FULL) = '1', in order to indicate FIFO saturation and

eventually read its content all at once.

If an overrun occurs, at least one of the oldest samples in FIFO has been overwritten and

the FIFO_OVR_IA flag in FIFO_STATUS2 (3Bh) is asserted.

In order to empty the FIFO before it is full, it is also possible to pull from FIFO the number of

unread samples available inFIFO_STATUS1 (3Ah) and FIFO_STATUS2

(3Bh)(DIFF_FIFO_[9:0]).

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