RTC.h

Purpose: Asynchronous Timer2 real-time counter support.

Namespace: atmega2560::rtc.

Timer2 may operate asynchronously from the crystal on PG4 (TOSC1) and PG3 (TOSC2). There is no separate dedicated calendar RTC peripheral.

#include <atmega2560/RTC.h>
 
namespace mcu = atmega2560;
 
static_assert(mcu::rtc::tosc1_pin_value == 0x64, "ATmega2560 RTC definition");

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

Source: ATmega2560 datasheet (DS40002211A).