CMA3000-D0X VTI Hamlin, CMA3000-D0X Datasheet - Page 17

• Manufacturer Part Number: CMA3000-D0X
• Description: Cma3000-d0x Series 3-axis Accelerometer
• Manufacturer: VTI Hamlin

4
4.1 SPI Interface
4.1.1
VTI Technologies Oy
www.vti.fi
Serial Interfaces
SPI frame format
Communication between the CMA3000 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
CMA3000 sensor: SPI and I
is done using the chip select signal. The I
register content. The CMA3000 acts as a slave on both the SPI and I
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 CMA3000 sensor
always operates as a slave device in master-slave operation mode. A typical SPI connection is
presented in Figure 6.
Figure 6. Typical SPI connection
The data transfer uses the following 4-wire interface:
CMA3000 SPI frame format and transfer protocol is presented in Figure 7.
Figure 7. SPI frame format
Each communication frame contains 16 bits. The first 8 bits in MOSI line contains info about the
register address being accessed and the operation (read/write). 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
followed by one zero bit. The later 8 bits in the MOSI line contain data for a write operation and are
MOSI
MISO
CSB
SCK
A5
1
A4
MICROCONTROLLER
SERIAL CLOCK (SCK)
2
MOSI
MISO
SCK
CSB
DATA OUT (MOSI)
DATA IN (MISO)
MASTER
A3
3
PORST
Doc.Nr. 8281000.12
A2
SS0
SS1
SS2
SS3
4
2
C (Phillips specification V2.1). Selection between these two interfaces
master out slave in
master in slave out
serial clock
chip select (low active)
A1
5
A0
6
RB/W
7
2
C interface can be also disabled by re-configuring
SI
SO
SCK
CS
SI
SO
SCK
CS
SI
SO
SCK
CS
SI
SO
SCK
CS
SLAVE
8
DO7
DI7
9
DO6
DI6
CMA3000 → µC
µC → CMA3000
µC → CMA3000
µC → CMA3000
10
DO5
DI5
11
2
DO4
C bus.
DI4
12
DO3
DI3
13
DO2
DI2
CMA3000-D0X Series
14
DO1
DI1
15
DO0
DI0
Rev. 0.12
16
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