PNI RM3100 Sensor Suite - Manual (Page 22)

PNI Sensor Corporation Doc 1017252 r03
RM3100 & RM2100 Sensor Suite User Manual Page 21 of 45
Sensor Drive and Measurement Pins (pins 6 – 13 & 15 – 18)
The various sensor drive and measurement pins should be connected to the sensor
coils. For a north-east-down (NED) reference frame, the connections should be as
defined in Figure 4-4.
I2CEN (pin 22)
This pin should be pulled LOW when using the SPI interface or pulled HIGH when
using the I
2
C interface.
DRDY (pin 23)
DRDY is used to ensure data is read from the MagI2C only when it is available. The
DRDY pin will go HIGH when the measurement is complete. This signals the host
that data is ready to be read. The DRDY pin automatically is set LOW when the
Measurement Result registers are read or a write operation is performed.
It is not mandatory to use the DRDY pin, as alternative methods exist to determine if
data is available. Specifically, the STATUS register provides this information. And,
if using the SPI interface where CPHA=CPOL=1, the MISO line also indicates if data
is available when SSN is LOW.
R
EXT
(pin 25)
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.
4.3.2 SPI Pins
MOSI (pin 1)
MOSI is an SPI input that provides data from the master device to the MagI2C. Data
is transferred most significant bit first. Data must be presented at least 50 ns before
the rising edge of SCLK, and remain valid for 50 ns after the edge. New data
typically is presented to the MOSI pin on the falling edge of SCLK.
SSN (pin 3)
This signal sets the MagI2C as the operating slave device on the SPI bus. The SSN
pin must be LOW prior to data transfer in either direction, and must stay LOW during
the entire transfer.
The SSN pin must transition from HIGH to LOW prior to reading from or writing to
the registers. It must stay LOW for the remainder of the operation.