Interfacing Digital to Analog converter 8085 microprocessor | 8085 Lab Program

 Section: Hardware Interfacing Experiments

Aim:

1. To write an assembly language program for digital to analog conversion.
2. To convert digital inputs into analog outputs & to generate different waveforms.

Apparatus Required:

• 8085 Microprocessor kit – 1
• Power Supply (+5 V dc, +12 V dc) – 1
• DAC Interface board – 1
• Cathode Ray Oscilloscope (CRO)

Algorithm:

• Measurement of Analog Voltage:

  1. Send the digital value to the DAC.
  2. Read the corresponding analog value at its output.

• Square Waveform Generation:

  1. Send low value (00H) to the DAC.
  2. Introduce a suitable delay.
  3. Send high value (0FH / FFH) to the DAC.
  4. Introduce delay.
  5. Repeat the above procedure continuously.

• Saw-tooth Waveform Generation:

  1. Load low value (00H) to accumulator.
  2. Send this value to DAC.
  3. Increment the accumulator.
  4. Repeat steps 2 and 3 until accumulator value reaches FFH.
  5. Repeat the procedure from step 1.

• Triangular Waveform Generation:

  1. Load low value (00H) in accumulator.
  2. Send accumulator content to DAC.
  3. Increment the accumulator.
  4. Repeat steps 2 and 3 until accumulator reaches FFH.
  5. Decrement the accumulator and send accumulator contents to DAC.
  6. Repeat step 5 until accumulator reaches 00H, then repeat from step 1.

---

Program:

• 1. Square Wave Program:

Address	Label	Mnemonics	Operand	Comment
4100	START	MVI	A, 00H	Load 00 in accumulator
4102		OUT	C8	Send through output port
4103		CALL	DELAY	Give a delay
4105		MVI	A, 0FH	Load 0F in accumulator
4107		OUT	C8	Send through output port
4108		CALL	DELAY	Give a delay
4109		JMP	START	Go to starting location
410A	DELAY	MVI	B, 05	Load count value 05 in B reg
410B	L1	MVI	C, 0F	Load count value 0F in C reg
410C	L2	DCR	C	Decrement C register
410E		JNZ	L2	Loop until C is 0
410F		DCR	B	Decrement B register
4110		JNZ	L1	Loop until B is 0
4112		RET		Return to main program

• 2. Saw-tooth Wave Program:

Address	Label	Mnemonics	Operand	Comment
4100	START	MVI	A, 00H	Load 00 in accumulator
4102	L1	OUT	C0	Send through output port
4103		INR	A	Increment contents of accumulator
4104		JNZ	L1	Send through output port until FF
4107		JMP	START	Go to starting location

• 3. Triangular Wave Program:

Address	Label	Mnemonics	Operand	Comment
4100	START	MVI	L, 00H	Load 00 in L register
4102	L1	MOV	A, L	Move contents of L to A
4103		OUT	C8	Send through output port
4104		INR	L	Increment contents of L
4105		JNZ	L1	Send through output port until FF
4108		MVI	L, FFH	Load FF in L register
4109	L2	MOV	A, L	Move contents of L to A
410A		OUT	C8	Send through output port
410B		DCR	L	Decrement contents of L
410C		JNZ	L2	Send through output port until 00
410F		JMP	START	Go to starting location

Observation:

• Measurement of Analog Voltage:

Digital Data	Analog Voltage
FF	5V
00	0V

Result: Thus digital to analog conversion is done and different waveforms such as square wave, sawtooth wave, and triangular wave are generated by interfacing DAC with 8085.

Viva Questions:

1. DAC (Digital to Analog Converter) finds application in what types of control systems?

2. Which device is connected between OUT1 and OUT2 of AD7523 to save DAC from negative transients?

3. What is the function of an operational amplifier connected at the output of AD7523?

4. What is the settling time of DAC 0800?

5. What is meant by the instruction `OUT C8`?

6. Give examples of various DAC ICs.

For all 2026 published articles list: click here: 
…till the next post, bye-bye & take care