; Lesson 5a - PIC Elmer lesson 5
; WB8RCR - 17 Nov 2003

		processor	16f84a
		include		<p16f84a.inc>
		__config	_HS_OSC & _WDT_OFF & _PWRTE_ON

; Variable Storage

		cblock		H'20'
			Spot1			; First program variable
			Spot2			; Second program variable
		endc

; Program code

Start
	;	Clear the status bits so we know their state
		bcf			STATUS,Z
		bcf			STATUS,C
		bcf			STATUS,DC

	;	Show how clrf affects the Z flag
		clrf		Spot1	; Clear out Spot1

	;	Show how a carry out of bit 7 affects the C flag
		movlw		H'f0'	; Store H'f0' in Spot2
		movwf		Spot2	;

		movlw		H'10'	; Add a H'10' to Spot2
		addwf		Spot2,W	; 

	;	Show how a carry out of bit 3 affects the DC flag
		movlw		D'15'	; Store a 15 (H'0f') in Spot2
		movwf		Spot2	;

		movlw		D'3'	; Add a 3 to Spot2
		addwf		Spot2,W	; 

	;	Set up a subtraction
		movlw		H'03'
		bsf			STATUS,C
		subwf		Spot2,F

		movlw		H'0f'
		subwf		Spot2,F

	; Look at AND and OR
		movlw		H'ee'
		andlw		H'e0'
		xorlw		H'e0'
		iorlw		H'f8'
		andwf		STATUS,F

	; Show increment and decrement
		clrw				; Clear out W and Spot1
		clrf		Spot1	;

		incf		Spot1,F	; Bump up Spot1 twice
		incf		Spot1,F	;

		decf		Spot2,F	; And bump down Spot2
		decf		Spot2,F	;

	; Lets do a counter
		clrf		Spot1
loop
		incfsz		Spot1,F
		goto		loop

    ; Bit testing
		movlw		D'03'
		movwf		Spot1
loop2
		clrw
		xorwf		Spot1,W
		btfsc		STATUS,Z
		goto		donebt
		decf		Spot1,F
		goto		loop2
donebt

	; Rock and roll
		movlw		B'01100010'
		movwf		Spot2
		movlw		H'f8'
		movwf		Spot1
loop3
		rlf			Spot2,F
		decfsz		Spot1,F
		goto		loop3

alldone
		goto		alldone	; Keep the simulator happy

		end					; And we're done