LSM303D Datasheet, PDF (24/52 Pages) STMicroelectronics – Embedded temperature sensor

Digital interfaces
LSM303D
Figure 6. Read and write protocol
CS
SPC
SDI
RW
DI7 DI6 DI5 DI4 DI3 DI2 DI1 DI0
MS AD5 AD4 AD3 AD2 AD1 AD0
SDO
DO7 DO6 DO5 DO4 DO3 DO2 DO1 DO0
AM10129V1
CS is the serial port enable and 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 is high (no transmission). SDI and SDO are
respectively the serial port data input and output. These 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 the 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 while the last bit (bit 15, bit 23, ...) starts at the last falling edge of SPC just
before the rising edge of CS.
bit 0: RW bit. When 0, the data DI(7:0) is written to the device. When 1, the data DO(7:0)
from the device is read. In the latter case the chip drives SDO at the start of bit 8.
bit 1: MS bit. When 0, the address remains unchanged in multiple read/write commands.
When 1, the address is auto-incremented in multiple read/write commands.
bit 2-7: address AD(5:0). 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 to 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 are added. When the MS
bit is 0, the address used to read/write data remains the same for every block. When the MS
bit is 1, the address used to read/write data is incremented at every block.
The function and the behavior of SDI and SDO remain unchanged.
24/52
DocID023312 Rev 2