SCA3000 Series
4
Serial Interfaces
Communication between the SCA3000 sensor and master controller is based on serial data
transfer and a dedicated interrupt line (INT-pin). Two different serial interfaces are available for the
SCA3000 sensor: SPI and I2C (Phillips specification V2.1). However, only one per product is
enabled by pre-programming in the factory. The SCA3000 acts as a slave on both the SPI and I2C
bus.
4.1 SPI Interface
SPI bus is a full duplex synchronous 4-wire serial interface. It consists of one master device and
one or more slave devices. The master is defined as a micro controller providing the SPI clock, and
the slave as any integrated circuit receiving the SPI clock from the master. The SCA3000 sensor
always operates as a slave device in master-slave operation mode. A typical SPI connection is
presented in Figure 5.
MASTER
MICROCONTROLLER
SLAVE
SI
DATA OUT (MOSI)
DATA IN (MISO)
SO
SERIAL CLOCK (SCK)
SCK
SS0
SS1
CS
SI
SS2
SS3
SO
SCK
CS
SI
SO
SCK
CS
SI
SO
SCK
CS
Figure 5. Typical SPI connection.
The data transfer uses the following 4-wire interface:
MOSI
MISO
SCK
master out slave in
master in slave out
serial clock
µC → SCA3000
SCA3000 → µC
µC → SCA3000
µC → SCA3000
CSB
chip select (low active)
4.1.1 SPI frame format
SCA3000 SPI frame format and transfer protocol is presented in Figure 6.
Figure 6. SPI frame format.
Each communication frame contains 16 bits. The first 8 bits in MOSI line contains info about the
operation (read/write) and the register address being accessed. The first 6 bits define the 6 bit
address for the selected operation, which is defined by bit 7 (‘0’ = read ‘1’ = write), which is
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