PNI RM3000-F Sensor Suite - Manual (Page 32)

PNI Sensor Corporation Doc #1016102 r04
RM3000-f & RM2000-f Sensor Suite User Manual Page 32
5.2.2 SAM Command Byte
The SAM Command Byte is defined as follows:
Bit # 7 6 5 4 3 2 1 0
Value 0 0 0 0 0 0 AS1 AS0
Table 5-2: SAM Axis Select Bits
Axis Measured AS1 AS0
No axis measured 0 0
X axis 0 1
Y axis 1 0
Z axis 1 1
5.2.3 Making a Single-Axis Measurement
The steps to make an interrupt-driven single X-axis sensor measurement are given below.
The 3D MagIC will return the result of a complete forward-reverse measurement of the
sensor in a 24-bit 2’s complement format (range: -8388608 to 8388607).
SSN pin is set LOW. This enables communication with the master device.
Send 0x01 on the MOSI pin to the 3D MagIC. This is the SAM Command Byte
to take a measurement on the X-axis sensor. Simultaneously, the 3D MagIC will
present a fixed 0x9A on the MISO pin. If the MISO pin reads 0x9B, then the 3D
MagIC is in Legacy Mode. Once the 8 bits have clocked in, the 3D MagIC will
execute the command (i.e. take a measurement).
The SSN input may be returned HIGH at this point to free up host communication
with another device if desired. This will not affect the measurement process.
A measurement is taken.
At the end of the measurement, the 3D MagIC will set the DRDY pin to HIGH,
indicating data is ready, and the 3D MagIC will enter Idle Mode.
The SSN input should be set LOW, if it is not already, to read the data.
The data is clocked out on the MISO pin with the next 24 clock cycles.
If another measurement is immediately made, SSN can remain LOW and the process
repeated. Otherwise it is recommended that SSN is set HIGH to release the SPI bus.