;Experiment-9 for "5x7 Video Screen" Project      
          ;PIC16F84 and only F84 chip         
          ;Column of LEDs moves across/back then up and down

Start   ORG 0x00
        BSF 03,5        ;Go to page1 for setting-up the ports	 
	MOVLW 00h       ;Put 00 into W     
	MOVWF 05h       ;Make all RA lines output    
        MOVWF 06h       ;Make all RB lines output
        BCF 03,5        ;Go to Page0 for programming
	GOTO Main

Back	BSF 05h,1
	BCF 05h,1	;Reset 4017 and allow 4017 to clock		
	MOVLW 00h
	MOVWF 06h	;Turn off LEDs to prevent "streaking"
	MOVF 19h,0	;Copy 19h into W
	MOVWF 18h	;Copy W into file 18h
Back1	CALL Clock
	DECFSZ 18h,1
	GOTO Back1
	MOVLW 7Fh
	MOVWF 06h	;Turn on all 7 LEDs
	CALL Delay
	RETURN


Scan	MOVLW 080h	;Determines the number of scans before 
	MOVWF 1Ch	; incrementing routine 
Scan1	BSF 05h,1        ;Reset 4017
        BCF 05h,1        ;allow 4017 to clock via clock line
	MOVLW 05h
	MOVWF 19h	;File 19h counts the number of columns
	
Scan2	CALL Short
	BCF 05,0	;Clock the 4017
	BSF 05,0
	DECFSZ 19h,1
	GOTO Scan2
	DECFSZ 1Ch,1
	GOTO Scan1
	RETURN
	

Clock	BCF 05,0	;Clock the 4017
	NOP
	BSF 05,0
	RETURN
	
Delay   MOVLW 03
        MOVWF 1Ah
Delay1  DECFSZ 1Bh,1
        GOTO Delay1
        DECFSZ 1Ch,1
        GOTO Delay1
        DECFSZ 1Ah,1
        GOTO Delay1
        RETURN

	;Short Delay

Short	DECFSZ 1Bh,1
	GOTO Short
	RETURN


	;Moves a colum of LEDs across the screen and back, 
	;then up and down the screen

Main   MOVLW 05
	MOVWF 19h	 ;Put 5 in the Count file for 5 columns
	BSF 05h,1        ;Reset 4017
        BCF 05h,1        ;allow 4017 to clock via clock line
	
Main1	MOVLW 7F
	MOVWF 06h	 ;Turn on 7 outputs for LEDs
	CALL Delay
	MOVLW 00	 ;Turn off LEDs to prevent mirroring
	MOVWF 06h
	CALL Clock	 ;Clock the 4017
	DECFSZ 19h,1	 ;Decrement the count file
	GOTO Main1

	MOVLW 03h
	MOVWF 19h	 ;3 shifts  - yes 3 shifts!
Main2	CALL Back
	DECFSZ 19h,1
	GOTO Main2
	BSF 05h,1
	BCF 05h,1	;Reset 4017
	CALL Delay	;This illuminates the first row!


	MOVLW 01
	MOVWF 06h	;Turn on first LED
	BCF 03h,0       ;clear the carry flag
Main3	CALL Scan
	RLF 06,1
	BTFSS 06,7	;When 8th! output is HIGH, program repeats	
	GOTO Main3

	MOVLW 20h
	MOVWF 06h
Main4	CALL Scan
	RRF 06,1
	BTFSS 06,0
	GOTO Main4
	CALL Scan	;This illuminates bottom row!
	GOTO Main	

        END