XC8 source code to test on μSim simulator (with Arduino Uno).

usim-demo-main.c

#include <xc.h>
#include <stdint.h>

// This is not an accurate frequency. The exact value may depend on the 
// specifications of the hosting platform.
#define _XTAL_FREQ 25000

void main(void) 
{    
    uint8_t position = 2;
    uint8_t direction = 1;
    
    // In Uno board PORTB[0] and PORTB[1] are used by UART.
    TRISB = 0x03;
    PORTB = 0x00;
            
    while(1)
    {                
        if(direction)
        {
            // Move LEDs in upward direction.
            position = position << 1;
        }
        else
        {
            // Move LEDs in downward direction.
            position = position >> 1;
        }
        
        PORTB = position;
        __delay_ms(250);
        
        // Direction changing.
        if(position <= 4)
        {
            direction = 1;
        }
        
        if(position >= 127)
        {
            direction = 0;
        }
    }
    
    return;
}