AT90LS4433-4AI datasheet(48/126 Pages) ATMEL

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AT90S/LS4433

1042H–AVR–04/03

Serial Peripheral

Interface – SPI

The Serial Peripheral Interface (SPI) allows high-speed synchronous data transfer

between the AT90S4433 and peripheral devices or between several AVR devices. The

AT90S4433 SPI features include the following:

• Full Duplex, Three-wire Synchronous Data Transfer

• Master or Slave Operation

• LSB First or MSB First Data Transfer

• Four Programmable Bit Rates

• End of Transmission Interrupt Flag

• Write Collision Flag Protection

• Wake-up from Idle Mode

Figure 36. SPI Block Diagram

The interconnection between Master and Slave CPUs with SPI is shown in Figure 37.

The PB5(SCK) pin is the clock output in the Master mode and is the clock input in the

Slave mode. Writing to the SPI Data Register of the Master CPU starts the SPI clock

generator, and the data written shifts out of the PB3(MOSI) pin and into the PB3(MOSI)

pin of the Slave CPU. After shifting one byte, the SPI clock generator stops, setting the

end of Transmission Flag (SPIF). If the SPI Interrupt Enable bit (SPIE) in the SPCR

select an individual Slave SPI device. The two Shift Registers in the Master and the

Slave can be considered as one distributed 16-bit circular Shift Register. This is shown

in Figure 37. When data is shifted from the Master to the Slave, data is also shifted in

the opposite direction, simultaneously. This means that during one shift cycle, data in

the master and the slave are interchanged.

AT90LS4433-4AI Datasheet(PDF) 48 Page - ATMEL Corporation