8085 Program to simulate decimal down counter

Now let us see a program of Intel 8085 Microprocessor. In this program we will see how to simulate the decimal down counter.

Problem Statement:

Write 8085 Assembly language program to simulate decimal down counter.

Discussion:

In this section we are simulating the decimal down counter. Here the counter will count 100 decimal numbers from 99 to 0. All values will be updated in each 0.5 seconds. For decimal count we are using the DAA instruction.

Note: Here for simplicity we are storing the numbers into memory. To simulate it like a counter we can use 7-segment display to show the numbers

Input:

Here we are not providing any input.

Flow Diagram:

Program:

Address	HEX Codes	Labels	Mnemonics	Comments
F000	3E, 99		MVI A,99H	Initialize A with 99H
F002	32, 00, 80	LOOP	STA 8000H	Store A into 8000H
F005	CD, 11, F0		CALL DELAY	Wait for 0.5 second
F008	3A, 00, 80		LDA 8000H	Get back the data from 8000H
F00B	C6, 99		ADI 99H	Add 99H with the number
F00D	27		DAA	Decimal adjust
F00E	C3, 02, F0		JMP LOOP	Jump to LOOP
F011	01, FF, FF	DELAY	LXI B,FFFFH	Initialize BC register pair to FFFFH
F014	0B	L1	DCX B	Decrease BC
F015	78		MOV A,B	Take B to A
F016	B1		ORA C	OR C and E
F017	C2, 13, F0		JNZ L1	If Z = 0, jump to L1
F01A	C9		RET	Return from subroutine