L99LD02 datasheet(28/66 Pages) STMICROELECTRONICS

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Serial peripheral interface (ST SPI standard)

L99LD02

28/66

DS12448 Rev 3

Serial peripheral interface (ST SPI standard)

The ST-SPI is a standard used in ST Automotive ASSP devices. Therefore the here

standardized SPI is described from SPI-Slave-Device point of view: a common structure of

the communication frames and specific addresses for product and status information are

defined.

The ST-SPI will allow usage of generic software to operate the devices while maintaining

the required flexibility to adapt it to the individual functionality of a particular product. In

addition to that, failsafe mechanisms are implemented to protect the communication from

external influences and wrong or unwanted usage.

5.1

Physical layer - Functional description

Figure 10. Physical layer

This device features a 32-bit ST SPI in slave configuration for bi-directional communication

with an external microcontroller. This device supports burst read access and shall be

operated in the following mode: CPOL = 0 and CPHA = 0.

For this mode, input data is sampled on the rising edge of the clock signal SCK and output

data is changed on the falling edge of SCK.

During standby mode, the SPI interface is deactivated.

Signal Description:



Chip Select Not (CSN)



The input pin is used to select the serial interface of this device. When CSN is high, the

output pin (SDO) will be in high-impedance state. In case CSN is stuck at GND, a

timeout is implemented which sets the SDO line back to high-impedance to release the

μC

SPI Master

L99LD02

SPI Slave

CSN

SCK

SDI

SDO

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