measure the xtal

[savnik]

I want to use timer0 in order to see in the LCD the frequency of crystal (internal clock). Or external on RA4
But I do not know how I begin.
I want use it , for measure xtal.

    ' 16F877A
    
   	DEFINE LCD_DREG	PORTD	      ' Selection of the port D
    DEFINE LCD_DBIT 4	          ' Selection one RD4 with RD7
    DEFINE LCD_RSREG PORTD	      ' RS on port D
    DEFINE LCD_RSBIT 2	          
    DEFINE LCD_EREG	PORTD         ' E on port D
    DEFINE LCD_EBIT 3	         
    DEFINE LCD_BITS 4		      ' Mode 4 bits
    DEFINE LCD_LINES 2	          ' 2 lines
      
    DEFINE OSC 4
       
    OPTION_REG = %00001000  
    
start:

    LCDOUT $FE,1,#TMR0
    
    goto start