Datasheet

MPL3115A2

Sensors

Freescale Semiconductor, Inc. 21

7.1.3 OUT_P_MSB (0x01), OUT_P_CSB (0x02), OUT_P_LSB (0x03), OUT_T_MSB (0x04),

OUT_T_LSB (0x05)

The Altitude data is stored as a signed fractional 20-bit value in meters in Q16.4 format. The OUT_P_MSB and OUT_P_CSB

registers contain the integer part in meters and the OUT_P_LSB register contains the fractional part. Left shifting the

OUT_T_MSB byte by 24 bits into a 32 variable and doing a logical OR with the OUT_T_CSB byte left shifted 16 bits and a logical

OR with the OUT_T_LSB byte left shifted 8 bits gives the altitude in meters times 65536.

The Pressure data is stored as an unsigned fractional 20-bit value in Pascals in Q18.2 format. The OUT_P_MSB and

OUT_P_CSB registers and bits 7-6 of the OUT_P_LSB register contain the integer part in Pascals. Bits 5-4 of OUT_P_LSB con-

tain the fractional component. Left shifting the OUT_T_MSB byte by 16 bits into a 32 variable and doing a logical OR with the

OUT_T_CSB byte left shifted 8 bits and a logical OR with the OUT_T_LSB byte gives the pressure in Pascals times 64.

When RAW bit is set (CTRL_REG1), then the RAW value is stored in all 24 bits of OUT_P_MSB, OUT_P_CSB and

OUT_P_LSB.

The Temperature data is stored as a signed fractional 12-bit value in °C in Q12.4 format. The OUT_T_MSB register contains

the integer part in °C and the OUT_T_LSB register contains the fractional part. Left shifting the OUT_T_MSB byte by 8 bits into

a 16-bit variable and adding the OUT_T_LSB byte with a logical OR gives the temperature in °C times 256. When RAW is se-

lected then the RAW value is stored in all 16 bits of OUT_T_MSB and OUT_T_LSB.

7.1.3.1 Data Registers with F_MODE = 00

The DR_STATUS register, OUT_P_MSB, OUT_P_CSB, OUT_P_LSB, OUT_T_MSB, and OUT_T_LSB are stored in the auto-

incrementing address range of 0x00 to 0x05. This allows the host controller to read the status register followed by the

20-bit Pressure/Altitude and 12-bit Temperature in a 6-byte, I

C transaction.

If the FIFO data output register driver is enabled (F_MODE > 00), register 0x01 points to the FIFO read pointer, while registers

0x02, 0x03, 0x04, 0x05, return a value of zero when read.

Table 14. OUT_P_MSB Register

7 6543210

R PD19 PD18 PD17 PD16 PD15 PD14 PD13 PD12

Reset00000000

Table 15. OUT_P_CSB Register

7 6543210

R PD11 PD10 PD9 PD8 PD7 PD6 PD5 PD4

Reset00000000

Table 16. OUT_P_LSB Register

7 6543210

R PD3 PD2 PD1 PD0 0 0 0 0

Reset00000000

Table 17. OUT_T_MSB Register

7 6543210

R TD11 TD10 TD9 TD8 TD7 TD6 TD5 TD4

Reset00000000

Table 18. OUT_T_LSB Register

7 6543210

RTD3 TD2 TD1 TD0 0 0 0 0

Reset00000000