AT90USB64/128
17. Serial Peripheral Interface – SPI
The Serial Peripheral Interface (SPI) allows high-speed synchronous data transfer between the
AT90USB64/128 and peripheral devices or between several AVR devices. The
AT90USB64/128 SPI includes the following features:
• Full-duplex, Three-wire Synchronous Data Transfer
• Master or Slave Operation
• LSB First or MSB First Data Transfer
• Seven Programmable Bit Rates
• End of Transmission Interrupt Flag
• Write Collision Flag Protection
• Wake-up from Idle Mode
• Double Speed (CK/2) Master SPI Mode
USART can also be used in Master SPI mode, see “USART in SPI Mode” on page 207.
The Power Reduction SPI bit, PRSPI, in “Power Reduction Register 0 - PRR0” on page 55 on
page 50 must be written to zero to enable SPI module.
Figure 17-1. SPI Block Diagram(1)
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Note:
1. Refer to Figure 1-1 on page 3, and Table 10-6 on page 81 for SPI pin placement.
The interconnection between Master and Slave CPUs with SPI is shown in Figure 17-2. The sys-
tem consists of two shift Registers, and a Master clock generator. The SPI Master initiates the
communication cycle when pulling low the Slave Select SS pin of the desired Slave. Master and
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ATMEL [ ATMEL ]
