2011-03-07

    .model small
    .data

    .stack
    .code


    ; procedura di inizializzazione della interrupt vector table
INIT_IVT    PROC
        PUSH    AX
        PUSH    BX
        PUSH    DX
        PUSH    DS
        XOR AX,     AX
        MOV DS,     AX

        ; channel 7
        MOV BX,     39
        SHL BX,     2
        MOV AX,     offset ISR_PA_IN
        MOV DS:[BX],    AX
        MOV AX,     seg ISR_PA_IN
        MOV DS:[BX+2],  AX
        ; channel 6
        MOV BX,     38
        SHL BX,     2
        MOV AX,     offset ISR_PA_OUT
        MOV DS:[BX],    AX
        MOV AX,     seg ISR_PA_OUT
        MOV DS:[BX+2],  AX
        ; channel 5
        MOV BX,     37
        SHL BX,     2
        MOV AX,     offset ISR_PB_IN
        MOV DS:[BX],    AX
        MOV AX,     seg ISR_PB_IN
        MOV DS:[BX+2],  AX
        ; channel 4
        MOV BX,     36
        SHL BX,     2
        MOV AX,     offset ISR_PB_OUT
        MOV DS:[BX],    AX
        MOV AX,     seg ISR_PB_OUT
        MOV DS:[BX+2],  AX
        ; channel 3
        MOV BX,     35
        SHL BX,     2
        MOV AX,     offset ISR_COUNT0
        MOV DS:[BX],    AX
        MOV AX,     seg ISR_COUNT0
        MOV DS:[BX+2],  AX
        ; channel 4
        MOV BX,     34
        SHL BX,     2
        MOV AX,     offset ISR_COUNT12
        MOV DS:[BX],    AX
        MOV AX,     seg ISR_COUNT12
        MOV DS:[BX+2],  AX

        POP DS
        POP DX
        POP BX
        POP AX
        RET
INIT_IVT    ENDP

; ISR for reading the value received on PA
ISR_PA_IN   PROC

            IRET
ISR_PA_IN   ENDP

; ISR for waiting a confirmation that the value written on PA is externally read
ISR_PA_OUT  PROC



            IRET
ISR_PA_OUT  ENDP

; ISR for reading the value received on PB
ISR_PB_IN   PROC
            IRET
ISR_PB_IN   ENDP

; ISR for waiting a confirmation that the value written on PB is externally read
ISR_PB_OUT  PROC

            IRET

ISR_PB_OUT  ENDP

; ISR executed when count0 ends
ISR_COUNT0  PROC

            IRET
ISR_COUNT0  ENDP


; ISR executed when count2 ends
ISR_COUNT12 PROC
            CMP CL,0
            JNE noread:
            IN  AL,080H
            XCHG AL,AH    ;AH diventa il mio nuovo "valore precedente"
            CMP  AL,AH    ; sottraggo il valore precedente(in AL) all'attuale  (in AH)
            JLE   noread:
            INC  CH



noread:     CMP CH,1
            JL  spenta
            MOV AL,0FFH
            OUT 081H,AL
            DEC CH
            JMP fine

spenta:     MOV AL,00H
            OUT 081H,AL


fine:       INC CL
            CMP CL,6
            JNE nores:
            MOV CL,0; CL gestito in maniera circolata
nores:
            IRET
ISR_COUNT12 ENDP

INIT_8255   PROC
            ; init 8255
            mov al, 10010000b;
            out 083h, al
            ; set PC4 to enable interrupt on PA in
            ;mov al, 00001001b
            ;out 083h, al
            ; set PC2 to enable interrupt on PB in or PB out
            ;mov al, 00000101b
            ;out 083h, al
            ; set PC6 to enable interrupt on PA out
            ;mov al, 00001101b
            ;out 083h, al
            RET
INIT_8255   ENDP

INIT_8253   PROC
            ;init 8253
            ;counter0 init
            ;mov al, 00110100b
            ;out 063h, al
             ;counter1 init
            mov al, 01110100b
            out 063h, al
             ;counter2 init
            mov al, 10010100b
            out 063h, al
             ;counter1 value
            mov ax,  10 ;tolgo 3 zero perche il simulatore inchioda
            out 061h, al
            xchg al,  ah
            out 061h, al
             ;counter2 value
            mov al,  30
            out 062h, al
            RET
INIT_8253   ENDP

; init 8259
INIT_8259   PROC
            PUSH DX
            PUSH AX
            MOV DX, 40H
            MOV AL, 00010011b  ; ICW1
            ; edge triggered
            ; single 8259
            ; IC4 = si
            OUT DX, AL
            MOV DX, 41H
            MOV AL, 00100000b  ; ICW2
            ; a partire da INTR 32
            OUT DX, AL
            MOV AL, 00000011b  ; ICW4
            ; fully nested mode
            ; buf mode
            ; master
            ; Automatic End Of Interrupt
            ;MOV AL, 00000001b  ; ICW4
            ; fully nested mode
            ; buf mode
            ; master
            ; normal End Of Interrupt
            OUT DX, AL
            MOV AL, 00000000b  ; OCW1
            ;no channel enabled
            MOV DX, 41H
            OUT DX, AL
            POP DX
            POP AX
            RET
INIT_8259   ENDP


;programma principale
            .startup
            CLI
            call INIT_IVT
            call INIT_8259
            call INIT_8253
            call INIT_8255
            XOR CX,CX
            XOR AX,AX
            STI


block:      ;hlt
            jmp  block

            .exit

            end  ; set entry point and stop the assembler.