Digital to Analog Conversion using 8255 (Programmable Peripheral Interface)

**************PROGRAM*******************
 DIGITAL TO ANALOG CONVERSION
**********************************************
1) SQUARE WAVE-
mov al,89                                    ;configure 8255
out 67,al                                      ;command address for 8255 - 67H
mov al,01                                    ;configure DAC (start of conversion)
out 63,al                                      ;command address for DAC- 63H
mov al,00
l1: out 61,al
    call delay
    mov al,FF
    out 61,al
    call delay
    jmp l1

2) RAMP WAVE-

mov al,89
out 67,al
mov al,01
out 63,al
mov al,00

l1: out 61,al

     inc al

     cmp al,FF

     jmp l1

3) STAIRCASE WAVE-

mov al,89
out 67,al
mov al,01
out 63,al
mov al,00

l1: out 61,al

     call delay

     add al,51

     cmp al,FF

     jnz l1

l2: out 61,al

     call delay

     sub al,51

     cmp al,00

     jnz l2

     jmp l1

4) TRAPEZOIDAL WAVE-

mov al,89
out 67,al
mov al,01
out 63,al
mov al,00

l1: out 61,al

     inc al

     cmp al,FF

     jne l1

out 61,al

call delay

l2: out 61,al

     dec al

     cmp al,00

     jne l2

     call delay

     jmp l1