ENG270 LAB5 EXP1

    list	p=18F1220
    radix	hex
    config	WDT=OFF, LVP=OFF, OSC=INTIO2;	Disable WDT, Low V Prog and RA6 as a clock

#include	p18f1220.inc	;Header file for SFR definitions

    count	equ		0x80
    count2	equ		0x81

    org		0x00
    GOTO	StartL		;Executes after reset

    org		0x08		;High priority
    GOTO	HIPRIO

    org		0x20		;Start the code

HIPRIO:
    BTFSC	PIR1, TMR1IF
    BRA		TIMERL		;If timer1 is interrupting then go to timer1 service routine
    RETFIE

TIMERL:
    BCF		T1CON, TMR1ON	;disable timer1

    ;Start of code to be executed during Timer1 interrupts
    TSTFSZ	count
    BRA		PWMplus10	    ;increment loop
    BRA		PWMminus10

PWMplus10:	;Adds 10% power
    MOVLW	.10
    ADDWF	CCPR1L
    INCF	count
    BRA		T1done

PWMminus10:	;subtracts 10% power
    MOVLW	.10
    SUBWF	CCPR1L
    INCF	count2
    TSTFSZ	count2
    BRA		T1done
    BTG		PORTB,3
    MOVLW	.252
    MOVWF	count
    MOVWF	count2
    BRA		T1done



T1done:		;get ready to return from interrupt
		;Reset Timer1 so next timer interrupt is in approximately 3 seconds
    MOVLW	0xD2
    MOVWF	TMR1H
    MOVLW	0x38
    MOVWF	TMR1L

    BCF		PIR1, TMR1IF	;clear timer1 interrupt flag
    BSF		T1CON, TMR1ON	;enable timer1
    RETFIE

StartL:		;entry point from reset
    ;Initialize all I/O ports
    CLRF	PORTA
    CLRF	PORTB
    MOVLW	0x7F
    MOVWF	ADCON1
    MOVLW	0x0D
    MOVWF	TRISA
    MOVLW	0xC7
    MOVWF	TRISB
    MOVLW	0x00
    ;Timer1 Initialization + interrupt enable/disable
    BSF		INTCON, PEIE	    ;enable peripheral interrupts
    BSF		PIE1, TMR1IE	    ;enable timer1 interrupt
    BSF		IPR1, TMR1IP	    ;set timer1 priority to high
    MOVLW	0x58		    ;Timer 1: "&&&-bit, osc. clock, 1:2 prescale, enabled, internal clk"
    MOVWF	T1CON
    ;Set timer 1 so next timer interrupt is in approx 3 seconds
    ;2 secx(10^6 usec/sec)x(sysClk/32usec)x(instClk/4sysClk)x(Tick/2 insClk) = 7812 Ticks
    ;set TMR1H & TMR1L TO [(2^16) - 7812 = 57725] OR (E17D) in hex
    MOVLW	0xD2
    MOVWF	TMR1H
    MOVLW	0x38
    MOVWF	TMR1L

    BSF		T1CON, TMR1ON	    ;Enable timer1
    BSF		INTCON, GIE	    ;Enable interrupts globally

    ;Following steps setup PWM
    MOVLW	0x00C		    ;"0000 1100
    MOVWF	CCP1CON		    ;PWM output on P1A Pin18

    CLRF	TMR2		    ;Timer2 register
    MOVLW	0x05		    ;Enable timer and set prescale to 4
    MOVWF	T2CON
    BCF		PIR1, TMR2IF	    ;clear timer2 flag

    MOVLW	.99
    MOVWF	PR2

    MOVLW	.0
    MOVWF	CCPR1L		    ;Set power level to 0%

    MOVLW	.252
    MOVWF	count
    MOVWF	count2

WAITL:
    BTFSS	PIR1, TMR2IF
    BRA		WAITL
    BCF		TRISB,3		    ;Set P1A/RB3/CCP1 as an output pin
    BSF		PORTB,5		    ;turn on LED just to indicate EDbot is on

MainL:		;waiting in a loop
    BRA		MainL

    end