LPS35HW Datasheet, PDF (15/48 Pages) STMicroelectronics – Embedded temperature compensation

LPS35HW
FIFO
4
FIFO
The LPS35HW embeds a 32-slot of 40-bit data FIFO to store the pressure and temperature
output values. This 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, Dynamic-Stream mode,
Stream-to-FIFO mode, Bypass-to-Stream and Bypass-to-FIFO mode. The FIFO buffer is
enabled when the FIFO_EN bit in CTRL_REG2 (11h) is set to '1' and each mode is
selected by the FIFO_MODE[2:0] bits in FIFO_CTRL (14h). Programmable FIFO threshold
status, FIFO overrun events and the number of unread samples stored are available in the
FIFO_STATUS (26h) register and can be set to generate dedicated interrupts on the
INT_DRDY pad using the CTRL_REG3 (12h) register.
FIFO_STATUS(FTH_FIFO) goes to '1' when the number of unread samples
(FIFO_STATUS(FSS5:0)) is greater than or equal to WTM[4:0] in FIFO_CTRL (14h). If
FIFO_CTRL(WTM4:0) is equal to 0, FIFO_STATUS(FTH_FIFO) goes to '0'.
FIFO_STATUS(OVRN) is equal to '1' if a FIFO slot is overwritten. FIFO_STATUS(FSS5:0)
contains stored data levels of unread samples; when FSS[5:0] is equal to '000000' FIFO is
empty, when FSS[5:0] is equal to '100000' FIFO is full and the unread samples are 32.
To guarantee the switching into and out of FIFO mode, discard the first sample acquired.
4.1
Bypass mode
In Bypass mode (FIFO_CTRL(FMODE2:0)=000), the FIFO is not operational and it
remains empty.
Bypass mode is also used to reset the FIFO when in FIFO mode.
As described in the next figure, for each channel only the first address is used. When new
data is available, the older data is overwritten.
Figure 6: Bypass mode
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