Example - 11hwint.asm Hardware Interrupts

; --------------------------------------------------------------

; An example of using hardware interrupts.

; This program spins the stepper motor continuously and

; steps the traffic lights on each hardware interrupt.
; Uncheck the "Show only one peripheral at a time" box

; to enable both displays to appear simultaneously.

JMP Start ; Jump past table of interrupt vectors

DB 50 ; Vector at 02 pointing to address 50
Start:

STI ; Set I flag. Enable hardware interrupts

MOV AL,11 ;

Rep:

ROR AL ; Rotate bits in AL right

JMP Rep

JMP Start

; --------------------------------------------------------------

ORG 50
PUSH al ; Save AL onto the stack.

PUSH bl ; Save BL onto the stack.

PUSHF ; Save flags onto the stack.

DB c8 ; Red+Amber Amber

DB 30 ; Green Red

DB 58 ; Amber Red+Amber

DB 57 ; Used to track progress through table

PastData:

MOV BL,[5B] ; BL now points to the data table

MOV AL,[BL] ; Data from table goes into AL

OUT 01 ; Send AL data to traffic lights

CMP AL,58 ; Last entry in the table

JZ Reset ; If last entry then reset pointer
INC BL ; BL points to next table entry

MOV [5B],BL ; Save pointer in RAM

JMP Stop

Reset:

MOV [5B],BL ; Save pointer into RAM location 54

Stop:

POPF ; Restore flags to their previous value

POP al ; Restore AL to its previous value

; --------------------------------------------------------------

; --------------------------------------------------------------

whilst at the same time counting from 0 to 9 repeatedly,

displaying the result on one of the seven segment displays.

If you want a harder challenge, count from 0 to 99 repeatedly

using both displays. Use the simulated hardware interrupt to

control the heater and thermostat.

steering the snake through the maze. Use the text characters

A, B, C Etc. to represent the disks. Use three of the four

rows on the simulated screen to represent the pillars.

30) Use the keyboard on Port 07. Write an interrupt handler

(INT 03) to process the key presses. You must also process

INT 02 (the hardware timer) but it need not perform any task.

For a more advanced task, implement a 16 byte circular buffer.

Write code to place the buffered text on the VDU screen when

you press Enter. For an even harder task, implement code to

process the Backspace key to delete text characters in the buffer.