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Microprocessor & Interfacing Lab Experiments

To generate positive going ramp (or sawtooth) using 8085 microprocessor.


To generate positive going ramp (or sawtooth) using 8085 microprocessor.

Apparatus:8085 microprocessor kit.

Theory:This program generates a stair case. If we continuously increment a 8 bit counter which is connected to ADC, then it will generate 255 voltage steps of a staircase at its analog output as the counter starts from 0 to 255. After 255th count , the counter returns to zero and again starts incrementing 0 to 255, so DAC generates 255 steps staircase (or ramp), which can be observed on the oscilloscope.

Procedure:There is a 26 pin connector J3. All the lines of 8255 PIO are brought out on this connector

The PIO cards are interfaced through 26 pin FRC flat cable.

  1. Connect the PIO card to DYNA -85L (J3) through 26 pin FRC flat cable as shown below:
  2. setup
  3. The program for all the PIO cards are given in an EPROM (2732) labeled PIO-MON. Place EPROM in socket U3 of DYNA_85L kit. Do the appropriate jumper setting for 2732 EPROM (Check DYNA-85L Manual for details).
  4. The Program can be entered in two ways:
  5. Copy the program from the specified RAM location as: DYNA-85> C 4E00 4EFF C000 Enter

    Enter the program given as below:

  6. Run the program from C000.

Code for display the message “Program for ramp generation”

C050: 0D 0A 50 52 4F 47 52 41 4D 20 46 4F 52 20 44 41

C060: 43 0D 0A 52 41 4D 50 20 47 45 4E 45 52 41 54 4F

C070: 52 00

[Press Enter]

Program:DYNA85LU> A C000 [Press Enter]

Address Opcode Label Mnemonics Remark
C000 21 50 C0 LXI H, C050 Load Message in HL
C002 CD 44 18 CALL 1844 Call display subroutine
C006 3E 89 MVI A,89h 8255 mode set to Mode 0
C008 D3 13 Out 13 8255 mode set to Mode 0
C00A 3E 01 MVI A,01 Initialize A with 01
C00C D3 11 OUT 11 Initialize A with 01
C00E 3C Up: INR A Increment step
C00F D3 10 Out 10 Output to DAC
C011 C3 0E C0 JMP up Go to label UP
C014 RST1 Hold the program
Press Enter Key
DYNA85LU> G C000 [Press Enter Key]





Time Period:

Result:The Sawtooth Waveform was generated and displayed on CRO as:



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