LSM320HAY30 datasheet(22/42 Pages) STMICROELECTRONICS

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Digital interfaces

LSM320HAY30

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Doc ID 16917 Rev 1

Data are transmitted in byte format (DATA). Each data transfer contains 8 bits. The number

of bytes transferred per transfer is unlimited. Data is transferred with the most significant bit

(MSb) first. If a receiver cannot receive another complete byte of data until it has performed

some other function, it can hold the clock line SCL LOW to force the transmitter into a wait

state. Data transfer only continues when the receiver is ready for another byte and releases

the data line. If a slave receiver does not acknowledge the slave address (i.e. it is not able to

receive because it is performing a real-time function) the data line must be left HIGH by the

slave. The master can then abort the transfer. A LOW to HIGH transition on the SDA line

while the SCL line is HIGH is defined as a STOP condition. Each data transfer must be

terminated by the generation of a STOP (SP) condition.

In order to read multiple bytes, it is necessary to assert the most significant bit of the sub-

address field. In other words, SUB(7) must be equal to 1 while SUB(6-0) represents the

address of the first register to be read.

In the presented communication format MAK is Master Acknowledge and NMAK is No

Master Acknowledge.

6.2

SPI bus interface

The LSM320HAY30 SPI is a bus slave. The SPI allows writing and reading of the registers

of the device.

The serial interface interacts with the outside world with 4 wires: CS, SPC, SDI and SDO.

Table 11.

Transfer when master is writing multiple bytes to slave

Master

SAD + W

SUB

DATA

Slave

SAK

Table 12.

Transfer when master is receiving (reading) one byte of data from slave

Master

SAD + W

SUB

SAD + R

NMAK

Slave

SAK

DATA

Table 13.

Transfer when master is receiving (reading) multiple bytes of data from slave

Master

ST SAD+W

SUB

SR SAD+R

MAK

NMAK

Slave

SAK

DATA

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