STGAP1STR datasheet(43/67 Pages) STMICROELECTRONICS

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STGAP1S

SPI interface

The IC communicates with an external MCU through a 16-bit SPI. This interface is used to

set the device parameters and for advanced diagnostic.

The SPI I/O pins are:



CS: chip select (active low)



CK: serial clock



SDI: serial data input (MOSI)



SDO: serial data output (MISO).

The interface is compliant with the SPI standard CPHA = 1 and CPOL = 0 (serial data is

sampled on CK falling edge and it is updated on CK rising edge, at CS falling edge the CK

signal must be low) as shown in Figure 20.

Figure 20. SPI timings

The SPI interface can work up to 5 Mbps and provides the daisy chain feature.

In order to guarantee a safe operation and robustness to electrical noise, the number of

rising edges within a CS negative pulse must be multiple of 16, otherwise the

communication cycle is ignored and a communication failure is indicated forcing high the

SPI_ERR flag.

Any number of the STGAP1S can be connected in daisy chain, and only 4 lines for the SPI

and one for the SD are required in order to guarantee access to status and configuration

registers of each device. An example of daisy chain configuration is shown in Figure 21.

SDI

SDO

MSB

LSB

N-1

N-2

MSB

HiZ

N-1

N-2

tsetCS

tenSDO

tsetSDI

tholSDI

tvSDO

tholSDO

tfCK

trCK

tlCK

thCK

tdisSDO

tholCS

tdesCS

MSB

tSDLCSL

tCSHSDH

(Not required for

NOP and read

operations)

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