Esame2012giu20.asm

;Exercise from June 20th, 2012 exam session
;Please note that only two of the four peripheral drivers are included in this solution.

org 400h
motore equ 0h             ;Moves elevator up and down
piano equ 1h              ;Elevator status flag: 0 = at kitchen, 1 = at dining room, 2 = moving in between
chiama0 equ 2h            ;Calls elevator to kitchen via interrupt
sensore0 equ 3h           ;Checks if elevator has reached kitchen via interrupt
chiama1 equ 4h            ;Calls elevator to dining room via interrupt
sensore1 equ 5h           ;Checks if elevator has reached dining room via interrupt
array equ 0AAAh           ;Stores 2B of data contaning floor flags
stato equ 0BBBh           ;Stores information concerning the elevator status
code
jsr init
seti
main: jmp main            ;Loops until interrupt
halt
init: push R0
push R1
movb #0, R0
movb #array, R1
movb R0, (R1)+            ;Initializes the array flags to zero
movb R0, (R1)
start chiama0             ;Starts all peripherals
start sensore0
start chiama1
start sensore1
pop R1
pop R0
ret
driver 2, 700h            ;Driver for "chiama0"
push R0
push R1
movl #piano, R0
cmpl #0, R0               ;Checks current elevator position
jz exitchiama             ;If elevator is already at kitchen floor, exits subroutine
cmpl #1, R0
jz muovi                  ;If elevator is at dining room floor, moves it
movl #array, R1
movb #1, R1               ;If elevator is already moving in between floors, sets kitchen array flag to 1
jmp exitchiama            ;Then exits
muovi: movl #stato, R1
movl #2, (R1)             ;Sets elevator status to "moving"
movl #0, R1
outl R1, motore           ;Motor is set to bring elevator down from dining room floor to kitchen floor
exitchiama: pop R1
pop R0
rti
driver 3, 900h            ;Driver for "sensore0"
push R0
push R1
movl #2, R0
outl R0, motore           ;Elevator is stopped (flag #2 = elevator not moving)
movl #array, R0
movl #0, (R0)+            ;Sets kitchen floor flag to zero
movl (R0), R1             ;Checks dining room floor flag
cmpl #0, R1
jz setflag                ;If flag equals zero, modifies it
movl #stato, R0
movl #2, R0               ;Sets elevator status to "moving"
movl #0, R0
outl R0, motore           ;Motor is set to bring elevator down from dining room floor to kitchen floor
jmp exitsens
setflag: movl #stato, R0
movl #0, (R0)             ;Kitchen floor flag is reset to 0
exitsens: pop R1
pop R0
rti
end