PNI RM3100 Sensor Suite - Manual (Page 34)

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RM3100 & RM2100 Sensor Suite User Manual Page 33 of 45
Since the registers are adjacent, it is not necessary to send multiple register addresses,
as the MagI2C automatically will read/write to the next adjacent register.
Relative Alarm Mode
In Relative Alarm Mode the limits for each axis initially are set by the Alarm Lower
Limit and Alarm Upper Limit value registers, as given in Table 5-5, similar to
Absolute Alarm Mode. However, when the ALARM bit is triggered and set HIGH,
the limit values are changed using the Alarm Hysteresis Values, given in Table 5-6.
Table 5-6: Alarm Hysteresis Registers
Register Description
Register
Name
Read
(Hex) Write
(Hex)
X Axis Alarm Hysteresis - MSB ADLX1 9E 1E
X Axis Alarm Hysteresis - LSB ADLX0 9F 1F
Y Axis Alarm Hysteresis - MSB ADLY1 A0 20
Y Axis Alarm Hysteresis - LSB ADLY0 A1 21
Z Axis Alarm Hysteresis - MSB ADLZ1 A2 22
Z Axis Alarm Hysteresis - LSB ADLZ0 A3 23
Since the registers are adjacent, it is not necessary to send multiple register addresses,
as the MagI2C automatically will read/write to the next adjacent register.
The new lower limit and upper limit values are defined as follows:
AUL = M + ADL
ALL = M – ADL
where AUL and ALL represent the new lower and upper limit register values, M is
the measured value that caused the ALARM bit to go HIGH, and ADL is the Alarm
Hysteresis Value.
Example of Absolute vs Relative Alarm Modes
Table 5-7 provides an example of how the Absolute and Relative Alarm Modes work
under the same conditions. This is illustrative purposes, and the MX readings would
depend on many things including the cycle count value and the magnetic field. In this