PNI RM3000 Sensor Suites - Manual (Page 27)

RM3000 & RM2000 Sensor Suite User Manual r08 Page 27 of 41
R
EXT
(External Timing Resistor)
R
EXT
ties to the external timing resistor for the high-speed clock. The recommended
value for the resistor and associated clock speed are defined in Table 3-1.
Sensor Drive and Measurement Pins
The various sensor drive and measurement pins should be connected to the
Geomagnetic Sensors. For a north-east-down (NED) reference frame, the
connections should be as defined in Figure 4-3.
4.4 SPI Timing Requirements
When implementing a SPI port, whether a dedicated hardware peripheral port or a software-
implemented port using general purpose I/O (also known as Bit-Banging), the timing
parameters (defined below in Figure 4-4 and specified in Table 4-2) must be met to ensure
reliable communication. Note that Standard Mode and Legacy Mode timing requirements
are identical with the exception of Legacy Mode utilizing the CLEAR line. The SPI clock
(SCLK) should run at 1 MHz or less. Generally data is considered valid while SCLK is
HIGH, and data is in transition when SCLK is LOW. The clock polarity used with the 3D
MagIC is zero (exclusively CPOL=0). Data is present on MISO or should be presented on
MOSI before the first low to high clock transition (exclusively CPHA = 0).
Figure 4-4: SPI Timing Diagram