PNI RM3100 Evaluation Board - Manual (Page 12)

PNI Sensor Corporation Doc 1017252 r02
RM3100 Evaluation Board User Manual Page 11 of 33
SI (pin 3)
SI, or more commonly MOSI (master output, slave input), is a SPI input providing
data from the host to the RM3100 Evaluation Board. Data is transferred most
significant bit first. Data must be presented at least 50 ns before the rising edge of
SCK, and remain valid for 50 ns after the edge. New data typically is presented to the
MOSI pin on the falling edge of SCK.
SSN (pin 4)
This signal sets the RM3100 Evaluation Board 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.
After communication between the RM3100 Evaluation Board and host is complete,
the SPI bus can be freed (SSN set HIGH) so the host may communicate with other
slave devices while the RM3100 Evaluation Board takes a measurement or is idle.
4.3.3 I
2
C Pins
SCL (pin 1)
SCL is used to synchronize the data sent between the RM3100 Evaluation Board
(slave) and the host system (master) on the SDA pin. SCL needs to be generated by
the host system and should be 1 MHz or less. Data is captured by the master device
on the rising edge of SCL. Data is shifted out and presented to the RM3100
Evaluation Board on the SDA pin on the falling edge of SCL, except for the first bit
which must be present before the first rising edge of SCL.
SDA (pin 3)
The SDA line is a bi-directional line used to send commands between the RM3100
Evaluation Board (slave) and the host system (master). Data is transferred most
significant bit first. All communication between the host and the RM3100 Evaluation
Board occurs on this line when implementing the I
2
C interface.
SA0 (pin 4)
SA0 represents the least significant bit in the between the RM3100 Evaluation
Board’s slave address. Pulling this HIGH represents a ‘1’ and pulling it low
represents a ‘0’. Along with pin 3 (bit 1) and the higher 5 bits (0b01000), which are