robot.asm

; multi-segment executable file template.

#start=robot.exe#  

r_port equ 9       
n_lamps equ 3

data segment
    ; add your data here!
    n_lamps_on db ?
    last_random db ?
ends

stack segment
    dw   128  dup(0)
ends

code segment
start:
; set segment registers:
    mov ax, data
    mov ds, ax
    mov es, ax

    ; add your code here
    
    mov n_lamps_on, 0
    mov last_random, 10
    
eternal_loop:    
    cmp n_lamps_on, n_lamps
    je finish 
    
    ; examine the area
    ; in front of the robot:
    mov al, 4
    out r_port, al
    
    call wait_exam
    
    ; nothing found?
    cmp al, 0
    je mover  ; - yes, so continue.
    
    ; wall?
    cmp al, 255  
    je mover  ; - yes, so continue.
    
    
    ; is lamp off?
    cmp al, 8
    je lamp_switch_on  
    
    jmp  mover  ; continue
    
lamp_switch_on:
    call switch_on_lamp
    inc n_lamps_on       
    
    jmp  mover  ; continue   
    
mover:
    call random_turn
    
    call wait_robot
    
    ; try to step forward:
    mov al, 1
    out r_port, al
    
    call wait_robot
    
    jmp eternal_loop ; go again!
    

finish:
    call wait_robot
    jmp finish

;===================================

; this procedure does not
; return until robot is ready
; to receive next command:
wait_robot proc
; check if robot busy:
busy: in al, r_port+2
      test al, 00000010b
      jnz busy ; busy, so wait.
ret    
wait_robot endp


;===================================
; this procedure does not
; return until robot completes
; the examination:
wait_exam proc   
mov cx,50
pausa:
    loop pausa   
; check if has new data:
busy2: in al, r_port+2
       test al, 00000001b
       jz busy2 ; no new data, so wait.
       in al, r_port+1
ret   
wait_exam endp
;===================================


;===================================

; switch off the lamp:
switch_off_lamp proc
    mov al, 6
    out r_port, al
    ret
switch_off_lamp endp

;===================================

; switch on the lamp:
switch_on_lamp proc
    mov al, 5
    out r_port, al
    ret
switch_on_lamp endp

;===================================

; generates a random turn using
; system timer:
random_turn proc
    
    ; get number of clock
    ; ticks since midnight
    ; in cx:dx
    mov ah, 0
    int 1ah
    
    ; randomize using xor:
    xor dh, dl
    xor ch, cl
    xor ch, dh
    
    cmp ch, last_random
    je random_turn
    mov last_random, ch
    
    test ch, 2
    jz no_turn
    
    test ch, 1
    jnz turn_right
    
    ; turn left:
    mov al, 2
    out r_port, al
    ; exit from procedure:
    ret  
    
turn_right:
    mov al, 3
    out r_port, al
    
no_turn:
    ret 
    
random_turn endp



ends

end start ; set entry point and stop the assembler.