Purpose: External interrupt and pin-change mappings.

Namespace: atmega2560::external_interrupts.

INT0..INT3 are on PD0..PD3. INT4..INT7 are on PE4..PE7. PCINT0..7 are PB0..7; PCINT8 is PE0 and PCINT9..15 are PJ0..PJ6; PCINT16..23 are PK0..PK7.

#include <atmega2560/ExternalInterrupts.h>
 
namespace mcu = atmega2560;
 
static_assert(mcu::external_interrupts::external_line_count == 8, "ATmega2560 ExternalInterrupts definition");
static_assert(static_cast<unsigned>(mcu::external_interrupts::PinChangePin::PCINT8) == 0x40, "PCINT8 on PE0");
static_assert(static_cast<unsigned>(mcu::external_interrupts::PinChangePin::PCINT23) == 0x97, "PCINT23 on PK7");

Interrupt pin groups

Hardware group	MCU pins
INT0–INT3	PD0–PD3
INT4–INT7	PE4–PE7
PCINT0–PCINT7	PB0–PB7
PCINT8	PE0
PCINT9–PCINT15	PJ0–PJ6
PCINT16–PCINT23	PK0–PK7

PCINT numbers and dedicated external interrupt lines are different resources.

These are hardware definitions, not runtime register access or initialization.

Source: ATmega2560 datasheet (DS40002211A).