Experiment-6

Exercises

Exercise-1

; Realize a 2-digit decimal down counter which counts down from 90 to 30 and
; then repeats. Display each count in the data field of the display for 0.5 sec.

START:
	MOV A, #90H 		; INITIALISE

ITER:
	MOV 60H, A 			; COPY DATA TO DISPLAY PLACEHOLDERS
	; LCALL UPDDT 		; DISPLAY PROGRAM
	MOV P2, A
	LCALL DELAY 		; AWAIT 0.5 SECONDS

	ADD A, #99H 		; ADD HUNDRED'S COMPLEMENT FORM
	DA A 				; DECIMALLY ADJUST ACCUMULATOR

	CJNE A, #29H, ITER 	; REPEAT DECREMENT. TILL (30D - 1), AND IN HEX

	SJMP START 			; REPEAT IN A LOOP

DELAY:
	; AWAIT (08H*0FAH*0FAH) MACHINE CYCLES => 0.5 SECONDS
	MOV R3, #08H
	UP1:
		MOV R4, #0FAH
		UP2:
			MOV R5, #0FAH
		DJNZ R4, UP2
	DJNZ R3, UP1

	RET 				; RETURN BACK TO THE MAIN LOOP
	END

Exercise-4

; Implement an 8 bit ring counter.

MOV A, #01H 			; INITIALISE

ITER:
	MOV 60H, A 			; COPY DATA TO DISPLAY PLACEHOLDERS
	LCALL UPDDT 		; DISPLAY PROGRAM
	LCALL DELAY 		; AWAIT

	RL A 				; LEFT SHIFT ACCUMULATOR, WITHOUT CARRY

	SJMP ITER 	 		; REPEAT IN A LOOP

DELAY:
	; AWAIT (04H*0FFH*0FFH) MACHINE CYCLES => ~0.26 SECONDS
	MOV R3, #04H
	UP1:
		MOV R4, #0FFH
		UP2:
			MOV R5, #0FFH
		DJNZ R4, UP2
	DJNZ R3, UP1

	RET 				; RETURN BACK TO THE MAIN LOOP
	END

Problems

Problem-1

; Implement an 8 - bit Octal up counter.

START:
	MOV A, #00H 		; INITIALISE
	MOV R2, #08H 		; FOR UPPER NIBBLE (OCTAL BASE)

ITER:
	MOV R1, #08H  		; FOR LOWER NIBBLE (OCTAL BASE)
	L_ITER:
		MOV 60H, A 		; COPY DATA TO DISPLAY PLACEHOLDERS
		PUSH A 			; SAVE ACCUMULATOR
		LCALL UPDDT 	; DISPLAY PROGRAM
		LCALL DELAY 	; AWAIT
		POP A 			; RETRIEVE ACCUMULATOR
		ADD A, #01H 	; INCREMENT LOWER NIBBLE
		DJNZ R1, L_ITER ; FOR LOWER NIBBLE UPDATES

	U_ITER:
		ADD A, #08H 	; INCREMENT UPPER NIBBLE
		DJNZ R2, ITER 	; FOR UPPER NIBBLE UPDATES

	SJMP START 			; REPEAT IN A LOOP

DELAY:
	; AWAIT (04H*0FFH*0FFH) MACHINE CYCLES => ~0.26 SECONDS
	MOV R3, #04H
	UP1:
		MOV R4, #0FFH
		UP2:
			MOV R5, #0FFH
		DJNZ R4, UP2
	DJNZ R3, UP1

	RET 				; RETURN BACK TO THE MAIN LOOP
	END

Problem-3

; Realize an 8-bit Johnson counter.

; LIMITATIONS: (1111 1111) AND (0000 0000) ARE REPEATED TWICE.

CLR C 					; CLEAR CARRY
MOV A, #00H 			; INITIALISE

ITER:
	MOV 60H, A 			; COPY DATA TO DISPLAY PLACEHOLDERS
	PUSH A 				; SAVE ACCUMULATOR
	LCALL UPDDT 		; DISPLAY PROGRAM
	LCALL DELAY 		; AWAIT
	POP A 				; RETRIEVE ACCUMULATOR

	CPL C 				; COMPLEMENT CARRY BIT
	RLC A 				; RIGHT SHIFT ACCUMULATOR

	SJMP ITER 			; REPEAT IN A LOOP

DELAY:
	; AWAIT (04H*0FFH*0FFH) MACHINE CYCLES => ~0.26 SECONDS
	MOV R3, #04H
	UP1:
		MOV R4, #0FFH
		UP2:
			MOV R5, #0FFH
		DJNZ R4, UP2
	DJNZ R3, UP1

	RET 				; RETURN BACK TO THE MAIN LOOP
	END