#include <pic16f84a.h>

typedef unsigned char uint8_t;

__sfr __at(0x70) UART_TX;
__sfr __at(0x71) UART_RX;
__sfr __at(0x72) UART_STATUS;

static volatile uint8_t _d0, _d1, _d2;

// Custom delay to make the output readable at 50MHz
static void delay(void) {
    _d0 = 0;
    do {
        _d1 = 0;
        do {
            _d2 = 0;
            do { _d2++; } while (_d2 != 0);
        } while (++_d1 != 50); // Increased for 50MHz visibility
        _d0++;
    } while (_d0 != 20);
}

static void uart_send(uint8_t byte) {
    while (UART_STATUS & 0x01); 
    UART_TX = byte;
}

static void uart_puts_rom(const char *s) {
    while (*s) {
        uart_send((uint8_t)*s);
        s++;
    }
}

// Simple BCD printer for 8-bit numbers
void print_uint8(uint8_t v) {
    uint8_t started = 0;
    
    // Hundreds
    if (v >= 200) { uart_send('2'); v -= 200; started = 1; }
    else if (v >= 100) { uart_send('1'); v -= 100; started = 1; }

    // Tens
    uint8_t tens = '0';
    while (v >= 10) { v -= 10; tens++; }
    if (started || tens != '0') { uart_send(tens); }

    // Units
    uart_send(v + '0');
}

void main(void) {
    uint8_t a, b, next;
    
    uart_puts_rom("\x1B[2J\x1B[H"); // Clear screen, Home cursor
    uart_puts_rom("PIC16F84A @ 50MHz Fibonacci\r\n");
    uart_puts_rom("---------------------------\r\n");

    while (1) {
        a = 0;
        b = 1;

        while (a <= 233) { // Max 8-bit Fib is 233
            print_uint8(a);
            uart_puts_rom(", ");

            next = a + b;
            a = b;
            b = next;

            delay();
            
            // Break before overflow
            if (a == 233) {
                print_uint8(a);
                break;
            }
        }
        
        uart_puts_rom("\r\nRestarting...\r\n");
        delay();
    }
}