PNI RM3100 Sensor Suite - Manual (Page 33)

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RM3100 & RM2100 Sensor Suite User Manual Page 32 of 45
There are two types of limits, Absolute and Relative. The LDM bit in the CMM register
establishes which type will be used, where “0” indicates Absolute and “1” indicates
Relative. In Absolute Alarm Mode, the limits are fixed and do not change, while in
Relative Alarm Mode the limits change whenever the current Alarm Limits are exceeded.
As the name suggests, Absolute Alarm Mode is used for monitoring the absolute
magnetic field, while Relative Alarm Mode is used to monitor changes in magnetic field.
Absolute Alarm Mode
In Absolute Alarm Mode the limits are set for each axis by the Alarm Lower Limit
and Alarm Upper Limit registers, as given in Table 5-5. The register values are
unsigned integers. The ALARM bit will go HIGH if the measured value (MX, MY,
or MZ) on any given axis is either greater than the Alarm Upper Limit for that axis or
less than the Alarm Lower Limit for that axis. This is an “OR” function, looking at
both the Alarm Upper and Lower Limits, and looking at all sensors being measured.
Table 5-5: Alarm Lower and Upper Limit Registers
Register Description
Register
Name
Read
(Hex) Write
(Hex)
X Axis Alarm Lower Limit - MSB ALLX2 8C 0C
X Axis Alarm Lower Limit - mid ALLX1 8D 0D
X Axis Alarm Lower Limit - LSB ALLX0 8E 0E
X Axis Alarm Upper Limit - MSB AULX2 8F 0F
X Axis Alarm Upper Limit - mid AULX1 90 10
X Axis Alarm Upper Limit - LSB AULX0 91 11
Y Axis Alarm Lower Limit - MSB ALLY2 92 12
Y Axis Alarm Lower Limit - mid ALLY1 93 13
Y Axis Alarm Lower Limit - LSB ALLY0 94 14
Y Axis Alarm Upper Limit - MSB AULY2 95 15
Y Axis Alarm Upper Limit - mid AULY1 96 16
Y Axis Alarm Upper Limit - LSB AULY0 97 17
Z Axis Alarm Lower Limit - MSB ALLZ2 98 18
Z Axis Alarm Lower Limit - mid ALLZ1 99 19
Z Axis Alarm Lower Limit - LSB ALLZ0 9A 1A
Z Axis Alarm Upper Limit - MSB AULZ2 9B 1B
Z Axis Alarm Upper Limit - mid AULZ1 9C 1C
Z Axis Alarm Upper Limit - LSB AULZ0 9D 1D