PNI RM3100 Evaluation Board - Manual (Page 19)

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RM3100 Evaluation Board User Manual Page 18 of 33
5.2 Initiate Continuous Measurement Mode (0x01)
The RM3100 Evaluation Board can either take measurements automatically on a regular
frequency (Continuous Measurement Mode) or by polling for single measurement. This
section discusses Continuous Measurement Mode. See Section 5.3 for polling a single
measurement.
To initiate Continuous Measurement Mode, write to the CMM register address, 0x01,
followed by the CMM register contents. To set the rate of data acquisition in Continuous
Measurement Mode, see Section 5.2.1. Below are the contents of the CMM register.
Bit # 7 6 5 4 3 2 1 0
Value LDM CMZ CMY CMX DRDM1 DRDM0 ALARM START
Where:
START – A “1” in this bit position initiates Continuous Measurement Mode. To turn
off Continuous Measurement Mode it is necessary to write a “0” to this bit position.
Note that writing to POLL (i.e. initiating a single measurement command) while
operating in Continuous Measurement Mode results in the single measurement
command being ignored.
ALARM – A feature of the RM3100 Evaluation Board while operating in Continuous
Measurement Mode is the ALARM bit will go HIGH if a measurement reading is
outside a predefined range of values, set by the Alarm Upper and Lower Limit
Registers. This bit is set to ‘1’ if a limit is exceeded. The ALARM bit is reset by
writing a ‘0’ to this bit. See Section 5.2.2 for additional information.
DRDM – These two bits establish the required condition to trigger the DRDY pin to
HIGH. There are 4 possible conditions, as set out in Table 5-3.