Programming Examples

Programming Examples

Example 10.5.1 Write a program to initialize counter 2 in mode 0 with a count of C030H. Assume address for control register = OBH, counter 0 = 08H, counter 1 = 09H and counter 2 = 0AH.

Solution : Control word :

Source Program :

MVI A, BOH

OUT 0BH ; Loads control word (B0H) the control register.

MVI A, lowbyte (30H)

OUT 0AH   ; Loads lower byte of the count.

MVI A, higher byte (C0H) ; Loads higher byte of the count.

OUT 0AH

Example 10.5.2 Write a program to generate a square wave of 1 kHz frequency on OUT 1 pin of 8253/54. Assume CLK1 frequency is 1 MHz and address for control register = 0BH, counter 1 = 09H and counter 2 = 0AH

Solution : To get square wave mode 3 is selected count should be 1 MHz          / 1 kHz = 1000

Control word :

Source program :

MVI A, 77H

OUT 0BH   ; Loads control word (77H) in the control register.

MVI A, Lowerbyte(00) ; Loads lower byte of the count

OUT 09H

MVI A, Higherbyte(10) ; Loads higher byte of the count

OUT 09H