PNI RM3000-F Sensor Suite - Manual (Page 33)

PNI Sensor Corporation Doc #1016102 r04
RM3000-f & RM2000-f Sensor Suite User Manual Page 33
5.3 Multi-Axis Measurement (MAM) Operation
An initial 2-byte command initiates a sensor measurement for up to 3 sensors. After
measurements are made and DRDY goes HIGH, another 1-byte command initiates reading of
the measured values on the MISO line. See the Appendix for code examples.
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 0x9A. If the Return Byte is 0x9B, then the 3D MagIC is
in Legacy Mode. 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 initial MAM Command Byte is sent to set up the 3D MagIC to take a sensor
measurement and a different MAM Command Byte is later sent to initiate reading the
measurement results registers on the MISO line. The MAM Command Byte is 0x82 to
set-up for a sensor measurement and 0xC9 to retrieve the data starting at the X axis. Note
the initial Command Byte (0x82) does not actually initiate a sensor measurement, as the
measurement is initiated after the MAM Axes Select Byte is sent.