LSM9DS1 Datasheet, PDF (31/72 Pages) –

LSM9DS1
Digital interfaces
5.2
Accelerometer and gyroscope SPI bus interface
The LSM9DS1 accelerometer and gyroscope SPI is a bus slave. The SPI allows to write
and read the registers of the device.
The Serial Interface connects to applications using 4 wires: CS_A/G, SPC, SDI and
SDO_A/G.
Figure 16. Accelerometer and gyroscope read and write protocol
&6B$*
&6
63&
6',
6'2B$*
6'2
5:
', ', ', ', ', ', ', ',
$' $' $' $' $' $' $'
'2 '2 '2 '2 '2 '2 '2 '2
CS_A/G is the serial port enable and it is controlled by the SPI master. It goes low at the
start of the transmission and goes back high at the end. SPC is the serial port clock and it is
controlled by the SPI master. It is stopped high when CS_A/G is high (no transmission). SDI
and SDO_A/G are respectively the serial port data input and output. Those lines are driven
at the falling edge of SPC and should be captured at the rising edge of SPC.
Both the read register and write register commands are completed in 16 clock pulses or in
multiples of 8 in case of multiple read/write bytes. Bit duration is the time between two falling
edges of SPC. The first bit (bit 0) starts at the first falling edge of SPC after the falling edge
of CS_A/G while the last bit (bit 15, bit 23, ...) starts at the last falling edge of SPC just
before the rising edge of CS_A/G.
bit 0: RW bit. When 0, the data DI(7:0) is written into the device. When 1, the data DO(7:0)
from the device is read. In latter case, the chip will drive SDO_A/G at the start of bit 8.
bit 1-7: address AD(6:0). This is the address field of the indexed register.
bit 8-15: data DI(7:0) (write mode). This is the data that is written into the device (MSb first).
bit 8-15: data DO(7:0) (read mode). This is the data that is read from the device (MSb first).
In multiple read/write commands further blocks of 8 clock periods will be added. When the
CTRL_REG8 (22h) (IF_ADD_INC) bit is ‘0’ the address used to read/write data remains the
same for every block. When the CTRL_REG8 (22h)(IF_ADD_INC) bit is ‘1’, the address
used to read/write data is increased at every block.
The function and the behavior of SDI and SDO_A/G remain unchanged.
DocID025715 Rev 3
31/72
72