STMPE811 datasheet(13/54 Pages) STMICROELECTRONICS

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STMPE811

SPI interface

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5.1.2

The following steps need to be followed for register write through SPI.

Assert CS_n by driving a '0' on this pin.

Drive a '0' on the first SCL launch clock on MOSI to select a write operation.

The next 7 bits on MOSI denote the 7-bit register address (MSB first).

The next byte on the MOSI denotes data to be written.

The following transmissions on MOSI are considered byte-sized data. The register

address to which the following data is written depends on whether the autoincrement

bit in the SPICON register is set. If this bit has been set previously, the register address

is incremented for data writes.

5.1.3

Termination of data transfer

A transfer can be terminated before the last launch edge by deasserting the CS_n signal. If

the last launch clock is detected, it is assumed that the data transfer is successful.

5.2

SPI timing modes

The SPI timing modes are defined by CPHA and CPOL,CPHA and CPOL are read from the

"SDAT" and "A0" pins during power-up reset. The following four modes are defined

according to this setting.

The clocking diagrams of these modes are shown in ON reset. The device always operates

in mode 0. Once the bits are set in the SPICON register, the mode change takes effect on

the next transaction defined by the CS_n pin being deasserted and asserted.

Table 8.

SPI timing modes

CPOL_N (SDAT pin)

CPOL

CPHA (ADDR pin)

Mode

0100

0111

1002

1013

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