Rainbow-electronics ATmega128L Uživatelský manuál stáhnout pdf (Strana 157)

157

ATmega128(L)

2467B–09/01

Serial Peripheral

Interface – SPI

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

between the ATmega128 and peripheral devices or between several AVR devices. The

ATmega128 SPI includes the following features:

• Full-duplex, 3-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

Figure 74. SPI Block Diagram

Note: Refer to Figure 1 on page 2, and Table 30 on page 69 for SPI pin placement.

The interconnection between Master and Slave CPUs with SPI is shown in Figure 75.

The system consists of two shift registers, and a Master clock generator. The SPI Mas-

ter initiates the communication cycle when pulling low the Slave Select SS

pin of the

desired Slave. Master and Slave prepare the data to be sent in their respective shift reg-

isters, and the Master generates the required clock pulses on the SCK line to

interchange data. Data is always shifted from Master to Slave on the Master Out – Slave

In, MOSI, line, and from Slave to Master on the Master In – Slave Out, MISO, line. After

each data packet, the Master will synchronize the Slave by pulling high the Slave Select,

, line.

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Rainbow-electronics ATmega128L Uživatelský manuál Strana 157