;*********************************************************************
;                                                                    *
;     	Tutorial 9 1ms Duty, 500Hz Signal using Timer0	             *    
;                                                                   *
;*********************************************************************
;*	TARGET PIC16F877
;*********************************************************************
;	Tests the Timer0 in Timer mode, with preload and prescalor,
;	
;	Expected Result.
;
;	PortB<0> to toggle high/low every 1ms, creating a 500Hz signal
;*********************************************************************
;*
;*	@version 	0.1, 20 September 2001
;*	@author		James Caska
;*********************************************************************


	list      p=16F877                   
	#include <p16F877.inc>               

	ORG	.0
	GOTO	INIT

;**********************************************************************
;* InterruptVector
;**********************************************************************
;* 	The Interrupt is called on Timer0 overflow
;**********************************************************************
	ORG	.4	
InterruptVector

	MOVLW	.1
	XORWF 	PORTB,F

	MOVLW	.6		;Preload (add) TMR0
	ADDWF	TMR0,F

	BCF	INTCON,T0IF	;Clear Timer0 Interrupt
	RETFIE


INIT


	;==========================================
	;Autogenerated configuration code PIC16F877
	;Config Wiz V0.1, www.virtualbreadboard.com
	;==========================================
	;======Begin PORT Configuration
	BSF STATUS, RP0	;PORT TRIS Registers are on page 1
	;======PORT B
	MOVLW   .0	;PORTB Configuration Bits
	MOVWF   TRISB
	BCF STATUS, RP0     ;Restore Page0


	;==========================================
	;Autogenerated configuration code PIC16F877
	;Config Wiz V0.1, www.virtualbreadboard.com
	;==========================================
	;======Begin Timer0 Configuration
	BSF STATUS, RP0	;Timer 0 config register on page 1
	;======Timer0 Timer Mode, uses Internal clock
	BCF OPTION_REG,T0CS	;T0CS: TMR0 Clock Source Select bit: 0 = Internal instruction cycle clock (CLKOUT)
	;======Timer0 Prescalor Configuration
	BCF OPTION_REG,PSA	;PSA: Prescaler Assignment bit:0 = Prescaler is assigned to the Timer0 module
	BSF OPTION_REG, PS0	;1:4
	BCF OPTION_REG, PS1
	BCF OPTION_REG, PS2
	BCF STATUS, RP0	;Restore page 1
	;======Timer0 Interrupt Configuration
	BCF INTCON, T0IF	;Timer 0 Clear Timer0 Interrupt flag
	BSF INTCON, T0IE	;Enabled Timer 0 Interrupt Mask
	;======End Timer0 Configuration



	CLRF	TMR0			;First shot not pre-loaded
	BSF 	INTCON,GIE		;Turn on the global interrupt
	
MAIN
	GOTO	MAIN



	END