LPS33HW datasheet(34/50 Pages) STMICROELECTRONICS

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LPS33HW

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Figure 20. “Threshold-based” interrupt event

If the AUTOZERO bit is set to '1', the measured pressure is used as a reference on the

PRESS_OUT (PRESS_OUT_H (2Ah), PRESS_OUT_L (29h) and PRESS_OUT_XL (28h))

are updated and the same value is also used for the interrupt generation:

–

PRESS_OUT = measured pressure - REF_P

After the first conversion the AUTOZERO bit is automatically set to '0'. To return back to

normal mode, the RESET_AZ bit has to be set to '1'. This resets also the content of the

REF_P registers.

If the AUTORIFP bit is set to '1', the measured pressure is used as a reference on the

(2Ah), PRESS_OUT_L (29h) and PRESS_OUT_XL (28h)) show the difference between the

measured pressure and the content of the RPDS registers (18h and 19h):

–

PRESS_OUT = measured pressure - RPDS*256

After the first conversion the AUTORIFP bit is automatically set to '0'. To return back to

normal mode, the RESET_ARP bit has to be set to '1'.

8.2

THS_P_L (0Ch)

Least significant bits of the threshold value for pressure interrupt generation.

The threshold value for pressure interrupt generation is a 16-bit unsigned right-justified

value composed of THS_P_H (0Dh) and THS_P_L (0Ch). The value is expressed as:

Interrupt threshold (hPA) = (THS_P) / 16.

To enable the interrupt event based on this user-defined threshold, the DIFF_EN bit in

INTERRUPT_CFG (0Bh) must be set to '1', the PHE bit or PLE bit (or both bits) in

INTERRUPT_CFG (0Bh) has to be enabled.

54321

THS7

THS6

THS5

THS4

THS3

THS2

THS1

THS0

THS[7:0]

This register contains the low part of threshold value for pressure interrupt generation.

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