PNI RM3100 Evaluation Board - Manual (Page 11)

PNI Sensor Corporation Doc 1017252 r02
RM3100 Evaluation Board User Manual Page 10 of 33
AVSS and DVSS (pins 7 & 14)
AVSS and DVSS should be tied to the analog and digital ground, respectively.
Assuming the ground plane is clean, they may share a common ground.
Alternatively, they may have their own ground planes if this is more convenient.
DVSS and AVSS should be within 0.1 V of each other.
DRDY (pin #5)
DRDY is used to ensure data is read from the RM3100 Evaluation Board 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.
I2CEN (pin #10)
This pin should be pulled LOW when using the SPI interface or pulled HIGH when
using the I
2
C interface.
4.3.2 SPI Pins
SCK (pin 1)
SCK is a SPI input used to synchronize the data sent in and out through the MISO
and MOSI pins. SCK is generated by the customer-supplied master device and
should be 1 MHz or less. One byte of data is exchanged over eight clock cycles.
Data is captured by the master device on the rising edge of SCK. Data is shifted out
and presented to the RM3100 Evaluation Board on the MOSI pin on the falling edge
of SCK, except for the first bit (MSB) which must be present before the first rising
edge of SCK.
SO (pin 2)
SO, or for more commonly MISO (master input, slave output), is a SPI output
transmiting data from the RM3100 Evaluation Board to the host. Data is transferred
most significant bit first and is captured by the master device on the rising edge of
SCK. The MISO pin is placed in a high impedance state if the RM3100 Evaluation
Board is not selected (i.e. if SSN=1).