Sensors

9

Freescale Semiconductor

MAG3110

See Figure 6 for details on how to perform read/write operations with MAG3110.

* Data Bytes Outgoing

* Data Bytes Incoming

4.3.2

Fast Read Mode

is set to skip over the LSB data. When FR bit is cleared, the complete 16-bit data is read accessing all 6 bytes sequentially

(OUT_X_MSB, OUT_X_LSB, OUT_Y_MSB, OUT_Y_LSB, OUT_Z_MSB, OUT_Z_LSB).

4.3.3

User Offset Corrections

The 2’s complement user offset correction register values are used to compensate for correcting the X, Y, and Z-axis after

device board mount. These values may be used to compensate for hard iron interference.

Depending on the setting of the RAW bit (CTRL_REG2, 0x11, bit 5) the magnetic field sample data is corrected with the user

offset values (RAW = 0), or can be read out uncorrected for user offset values (RAW = 1). The factory calibration correction is

always applied irrespective of the setting of the RAW bit.

The factory calibration for gain, offset and temperature compensation is always automatically applied irrespective of the setting

of the RAW bit which only controls the subtraction of the user defined hard iron offset.

4.3.4

INT1

The DR_STATUS register (see section 5.1.1) contains the ZYXDR bit which denotes the presence of new measurement data

on one or more axes. Software polling can be used to detect the transition of the ZYXDR bit from 0 to 1 but, since the ZYXDR bit

is also logically connected to the INT1 pin, a more efficient approach is to use INT1 to trigger a software interrupt when new

measurement data is available as follows:

1. Put MAG3110 in ACTIVE mode (CTRL_REG1 = 0bXXXXXX01).

2. Idle until INT1 goes HIGH and activates an interrupt service routine in the user software.

3. Read magnetometer data as required from registers 0x01 to 0x06. INT1 is cleared when register 0x01 OUT_X_MSB is

read and this register must therefore always be read in the interrupt service routine.

4. Return to idle in step 2.

4.3.5

Triggered Measurements

Set the TM bit in CTRL_REG1 when you want the part to acquire only 1 sample on each axis. See table below for details.

Single/Burst Write Operation

IIC Start

IIC Slave ADDR

(R/W bit = 0)

MAG3110 Register Address to Start Write

Data0*

Data1

—

IIC

STOP

Single/Burst Read Operation

IIC Start

IIC Slave ADDR

(R/W bit = 0)

MAG3110 Register Address to Start Read

IIC Repeated Start

IIC Slave ADDR

(R/W bit = 1)

Data0*

Data1

—

IIC

STOP

AC

TM

Description

0

0

ASIC is in low power standby mode.

0

1

The ASIC shall exit standby mode, perform one measurement cycle based on

enter standby mode.

1

0

The ASIC shall perform continuous measurements based on the current OSR

and ODR settings.

1

1

The ASIC shall continue current measurement at fastest applicable ODR for

programmed OSR. The ASIC shall return to programmed ODR after completing

the triggered measurement.