I/O registers and port operations of AVR microcontrollers-EEWORLD

1. The macro "_BV(bit)" defined in the header file "sfr_defs.h" is also often used to implement bit operations.

Among them, the macro "_BV(bit)" is defined as:

#define _BV(bit) (1<<(bit))

example:

DDRD = _BV(PD0) | _BV(PD1)

//In ioxxxxxxx.h of the corresponding device, PD0 is defined as 0 and PD1 is defined as 1

Therefore, DDRD = _BV(PD0) | _BV(PD1) is equivalent to DDRD=0x03.

2. Each I/O port of ATmega128 has 3 registers to control, namely:

Direction register DDRx, data register PORTx and input pin register PINx.

Among them, the direction register DDRx and the data register PORTx are readable and writable registers, while PINx is a read-only register.

example:

When performing a write operation, the direction register DDRB is used to specify whether the PB port is used as an input port or an output port;

When performing a read operation, the direction setting value of the port is read from the direction register DDRB.

DDRA = 0xFF; //Initialize port A to output mode.

#define LED0 0

#define LED1 1

DDRC = 0xFF;

PORTC = 0xFF;

...

PORTC &= ~ _BV (LED0); // Output low level

PORTC | = _BV (LED1); //output high level

...

PORTC &= ~ _BV (LED1); // Output low level

PORTC | = _BV (LED0); //output high level

SPDR: SPI Data Register

SPSR: SPI Status Register

SPCR: SPI Control Register

Reference address：I/O registers and port operations of AVR microcontrollers

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