LPS25HB datasheet(14/40 Pages) STMICROELECTRONICS

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FIFO

LPS25HB

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DocID027112 Rev 2

FIFO

The LPS25HB embeds 32-slot data FIFO to store the pressure output values. The FIFO

allows consistent power saving for the system, since the host processor does not need to

continuously poll data from the sensor, but it can wake up only when needed and burst the

significant data out from the FIFO.

This buffer can work according to seven different modes: Bypass mode, FIFO mode, Stream

mode, Stream-to-FIFO mode, Bypass-to-Stream mode, Bypass-to-FIFO mode and FIFO

Mean mode.

The FIFO buffer is enabled when the FIFO_EN bit in CTRL_REG2 (21h) is set to '1' and

each mode is selected by the F_MODE[2:0] bits in FIFO_CTRL (2Eh).

FIFO threshold status, FIFO overrun events and the number of unread samples stored are

available in the FIFO_STATUS (2Fh) register and can be set to generate dedicated

interrupts on the INT_DRDY pin in the CTRL_REG4 (23h) register.

4.1

Bypass mode

In Bypass mode (F_MODE[2:0] in FIFO_CTRL (2Eh) set to '000'), the FIFO is not

operational and it remains empty.

4.2

FIFO mode

In FIFO mode (F_MODE[2:0] in FIFO_CTRL (2Eh) set to '001'), the data from

PRESS_OUT_H (2Ah), PRESS_OUT_L (29h), and PRESS_OUT_XL (28h) are stored in

the FIFO.

A watermark interrupt can be enabled (STOP_ON_FTH bit set to '1' in CTRL_REG2 (21h))

in order to be raised when the FIFO is filled to the level specified by the WTM_POINT[4:0]

bits of FIFO_CTRL (2Eh). The FIFO continues filling until it is full (32 slots of data for

pressure output). When full, the FIFO stops collecting data.

4.3

Stream mode

In Stream mode (F_MODE[2:0] in FIFO_CTRL (2Eh) set to '010'), the data from

PRESS_OUT_H (2Ah), PRESS_OUT_L (29h), and PRESS_OUT_XL (28h) are stored in

the FIFO. The FIFO continues filling until it's full (32 slots of data for pressure output). When

full, the FIFO discards the older data as the new arrive. A watermark interrupt can be

enabled and set as in FIFO mode.

4.4

Stream-to-FIFO mode

In Stream-to-FIFO mode (F_MODE[2:0] in FIFO_CTRL (2Eh) set to '011'), the data from

PRESS_OUT_H (2Ah), PRESS_OUT_L (29h) PRESS_OUT_L (29h) and PRESS_OUT_XL

(28h) are stored in the FIFO.

A Watermark interrupt can be enabled (STOP_ON_FTH bit set to '1' in CTRL_REG2 (21h))

in order to be raised when the FIFO is filled to the level specified by the WTM_POINT[4:0]

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