AVR128DB48 MVIO status bit test

// by Ido Gendel, 2021
// Share and enjoy!

// Target: AVR128DB48 Curiosity Nano evaluation kit
// Using: MPLAB X 5.45, XC8 2.30

#include <xc.h>
#include <avr/io.h>
#include <avr/interrupt.h>

FUSES = {
    .WDTCFG = 0x00, // WDTCFG {PERIOD=OFF, WINDOW=OFF}
    .BODCFG = 0x00, // BODCFG {SLEEP=DISABLE, ACTIVE=DISABLE, SAMPFREQ=128Hz, LVL=BODLEVEL0}
    .OSCCFG = 0xF8, // OSCCFG {CLKSEL=OSCHF}
    .SYSCFG0 = 0xD2, // SYSCFG0 {EESAVE=CLEAR, RSTPINCFG=GPIO, CRCSEL=CRC16, CRCSRC=NOCRC}
    .SYSCFG1 = 0xE8, // SYSCFG1 {SUT=0MS, MVSYSCFG=DUAL}
    //.SYSCFG1 = 0xF0, // SYSCFG1 {SUT=0MS, MVSYSCFG=SINGLE}
    .CODESIZE = 0x00, // CODESIZE {CODESIZE=User range:  0x0 - 0xFF}
    .BOOTSIZE = 0x00, // BOOTSIZE {BOOTSIZE=User range:  0x0 - 0xFF}
};
LOCKBITS = 0x5CC5C55C; // {KEY=NOLOCK}

inline void LEDasVDDIO2(void) {

  // The on-board LED is negative logic
  if (MVIO_STATUS & 1) PORTB_OUTCLR = 8;
    else PORTB_OUTSET = 8;

}

void main(void) {

    PORTB_DIRSET = 8; // PB3 is the on-board LED
    LEDasVDDIO2(); // Reflect the initial status, until an interrupt occurs

    // PC0 as output HIGH for testing under current draw
    PORTC_DIRSET = 1;
    PORTC_OUTSET = 1;

    MVIO_INTCTRL |= 1; // Enable the MVIO interrupt
    CPU_SREG |= 0x80; // Enable global interrupts

    for ( ; ; ) {
    }
    return;

}

ISR(MVIO_MVIO_vect) {
  LEDasVDDIO2();
  MVIO_INTFLAGS = 1; // Clear flag - this one's not automatic!
}