Scoreboard display on LCD (edsim51)

[Reiniku]

Hello! I'm currently learning the basics of microcontrollers and was given the task of creating a scoreboard to display on the LCD (so 4 digits) and have switches to increment and decrement each displayed digit in assembly. So something like:

0000

Switch 1 and 2, decrements and increments the first digit, 3 and 4 for the second... so on and so forth.

Hitting switch 2 from this point would show: 1000

Switch 4 woudl show: 1100

Etc.

I've figure out how to output to the LCD (thanks to the edsim51 examples) so that my program shows "0000" when run, but I'm not sure how to implement the rest of my code.

I'm not asking how to be spoon fed how to do it but more like I could use some guidance. Would it be possible to use the "switch banks" on the screen to do this? There ARE 8 of them. And do I have to use interrupts to increment and decrement the counters?

If it's of any help here's the code I have written to display "0000" on the LCD:

; put data in RAM
	MOV 30H, #'0'
	MOV 31H, #'0'
	MOV 32H, #'0'
	MOV 33H, #'0'
	MOV 34H, #0; end of data marker


; initialise the display
; see instruction set for details


	CLR P1.3		; clear RS - indicates that instructions are being sent to the module

; function set	
	CLR P1.7		; |
	CLR P1.6		; |
	SETB P1.5		; |
	CLR P1.4		; | high nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	CALL delay		; wait for BF to clear	
					; function set sent for first time - tells module to go into 4-bit mode
; Why is function set high nibble sent twice? See 4-bit operation on pages 39 and 42 of HD44780.pdf.

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E
					; same function set high nibble sent a second time

	SETB P1.7		; low nibble set (only P1.7 needed to be changed)

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E
				; function set low nibble sent
	CALL delay		; wait for BF to clear


; entry mode set
; set to increment with no shift
	CLR P1.7		; |
	CLR P1.6		; |
	CLR P1.5		; |
	CLR P1.4		; | high nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	SETB P1.6		; |
	SETB P1.5		; |low nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	CALL delay		; wait for BF to clear


; display on/off control
; the display is turned on, the cursor is turned on and blinking is turned on
	CLR P1.7		; |
	CLR P1.6		; |
	CLR P1.5		; |
	CLR P1.4		; | high nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	SETB P1.7		; |
	SETB P1.6		; |
	SETB P1.5		; |
	SETB P1.4		; | low nibble set

	SETB P1.2		; |
	CLR P1.2		; | negative edge on E

	CALL delay		; wait for BF to clear


; send data
	SETB P1.3		; clear RS - indicates that data is being sent to module
	MOV R1, #30H	; data to be sent to LCD is stored in 8051 RAM, starting at location 30H
loop:
	MOV A, @R1		; move data pointed to by R1 to A
	JZ finish		; if A is 0, then end of data has been reached - jump out of loop
	CALL sendCharacter	; send data in A to LCD module
	INC R1			; point to next piece of data
	JMP loop		; repeat

finish:
	JMP $


sendCharacter:
	MOV C, ACC.7		; |
	MOV P1.7, C			; |
	MOV C, ACC.6		; |
	MOV P1.6, C			; |
	MOV C, ACC.5		; |
	MOV P1.5, C			; |
	MOV C, ACC.4		; |
	MOV P1.4, C			; | high nibble set

	SETB P1.2			; |
	CLR P1.2			; | negative edge on E

	MOV C, ACC.3		; |
	MOV P1.7, C			; |
	MOV C, ACC.2		; |
	MOV P1.6, C			; |
	MOV C, ACC.1		; |
	MOV P1.5, C			; |
	MOV C, ACC.0		; |
	MOV P1.4, C			; | low nibble set

	SETB P1.2			; |
	CLR P1.2			; | negative edge on E

	CALL delay			; wait for BF to clear

delay:
	MOV R0, #50
	DJNZ R0, $
	RET