Sensors

13

Freescale Semiconductor

MAG3110

5.2

Device ID

5.2.1

WHO_AM_I (0x07)

Device identification register. This read-only register contains the device identifier which is set to 0xC4. This value is factory

programmed. Consult factory for custom alternate values.

5.2.2

SYSMOD (0x08)

The read-only system mode register indicates the current device operating mode.

5.3

User Offset Correction

5.3.1

OFF_X_MSB (0x09), OFF_X_LSB (0x0A), OFF_Y_MSB (0x0B), OFF_Y_LSB (0x0C),

OFF_Z_MSB (0x0D), OFF_Z_LSB (0x0E)

X-axis, Y-axis, and Z-axis user defined offsets in 2's complement format which are used when RAW = 0 (see section 5.5.2) to

correct for the MAG3110 zero flux offset and for hard iron offsets on the PCB caused by external components. The maximum

sensible range for the user offsets is in the range -15,000 to 15,000 bit counts comprising the sum of the correction for the zero

flux offset (range -500

μT to 500 μT or -5000 to 5000 bit counts) and the PCB hard iron offset (range -1000 μT to 1000 μT or

-10,000 to 10,000 bit counts).

The user offsets are automatically subtracted by the MAG3110 logic when RAW = 0 before the magnetic field readings are

written to the data measurement registers 0x01 to 0x06. The maximum range of the X, Y and Z data measurement registers when

RAW = 0 is therefore -30,000 to 30,000 bit counts and is computed without clipping. The user offsets are not subtracted when

RAW = 1. The least significant bit of the user defined X, Y and Z offsets is forced to be zero irrespective of the value written by

the user.

If the MAG3110 zero flux offset and PCB hard iron offset corrections are performed by an external microprocessor (the most

likely scenario) then the user offset registers can be ignored and the RAW bit should be set to 1.

The user offset registers should not be confused with the factory calibration corrections which are not user accessible and

which are always applied to the measured magnetic data.

Table 18. WHO_AM_I Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

110

0

0100

Table 19. SYSMOD Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

00000

0

SYSMOD1

SYSMOD0

Table 20. SYSMOD Description

SYSMOD

System Mode. Default value: 00.

00: STANDBY mode.

01: ACTIVE mode, RAW data.

10: ACTIVE mode, non-RAW user-corrected data.

Table 21. OFF_X_MSB Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

XD14

XD13

XD12

XD11

XD10

XD9

XD8

XD7

Table 22. OFF_X_LSB Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

XD6

XD5

XD4

XD3

XD2

XD1

XD0

0

Table 23. OFF_Y_MSB Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

YD14

YD13

YD12

YD11

YD10

YD9

YD8

YD7

Table 24. OFF_Y_LSB Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

YD6

YD5

YD4

YD3

YD2

YD1

YD0

0