PNI RM3000 Sensor Suites - Manual (Page 33)

RM3000 & RM2000 Sensor Suite User Manual r08 Page 33 of 41
5.3 Multi-Axis Measurement (MAM) Operation
An initial MAM Command Byte initiates a sensor measurement for up to 3 sensors. After
the measurements are made and the DRDY line goes HIGH, another MAM Command Byte
sets up the 3D MagIC to output the measured values on the MISO line.
5.3.1 MAM SPI Activity Sequence
The SPI timing sequence is given below for MAM operation. SPI timing is discussed in
Section 4.4. The Return Byte is 9A
H
. The number of data bytes will be determined by
the number of axes that are to be measured. Each axis is comprised of 3 bytes of data, so
for a 3 axis measurement 9 total bytes would be clocked out to receive all the data. The
Command Byte and Axes Select Byte are discussed below.
Figure 5-2: SPI Activity Sequence Diagram for MAM Operation
5.3.2 MAM Command Byte
The MAM Command Byte either initiates a sensor measurement or initiates placing the
measurement results on the MISO line for the host to read. The MAM Command Byte is
82
H
to initiate a sensor measurement and is C9
H
to retrieve the data.
Note: Measurement results are stored in registers within the 3D MagIC. If SCLK continues to
run after the appropriate number of data bytes for the defined number of axes to be measured,
then the information on the MISO line will have little meaning. SCLK should be stopped once the
measurements are clocked out.