STGAP1AS datasheet(44/70 Pages) STMICROELECTRONICS

44 / 70 page

SPI interface

STGAP1AS

44/70

DocID029344 Rev 2

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.

SPI commands are executed after the rising edge of the CS, and adequate wait time must

be respected before a new command is started by setting the CS low again. Refer to the

tdesCS parameter in Table 6 on page 14 for required wait time after each command.

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 the 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 STGAP1AS 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.

In case that several STGAP1AS devices are connected in the SPI link, each of them can be

configured in a different way by simply writing the desired data in each configuration and

diagnostic register. This allows for example differentiating the configuration for high-side

and low-side drivers.

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)

STGAP1AS Datasheet(PDF) 44 Page - STMicroelectronics

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