;*************************************************************
;ISRSETUP.ASM   -  A program setting up an interrupt servive routine 
;                  as a Teminate-and-Stay-Resident (TSR) Program, which 
;                  can be called using Interrupt Request 72h            
;*************************************************************
 
.MODEL small
.STACK 200h   
 
.DATA
MASTR0 equ 20h
MASTR1 equ 21h
SLAVE0 equ 0A0h
SLAVE1 equ 0A1h
 
 
.CODE
 
main: 
jmp start
 
ToBeExec Proc Far
Pushf
Push dx         ;places (pushes) content of register ax onto stack
push ax         ;places (pushes) content of register dx onto stack        
push bx
push cx
 
sti
    mov     cx,2000                 ;1st beep tone frequency
    ;call    beep                    ;go sound the beep
;beep:
    mov     al,10110110b                    ;load control word
    out     43h,al                          ;send it
    mov     ax,cx                           ;tone frequency into AX
    out     42h,al                          ;send LSB
    mov     al,ah                           ;move MSB to AL
    out     42h,al                          ;send it
    in      al,61h                          ;get port 61 state
    or      al,00000011b                    ;turn on speaker
    out     61h,al                          ;speaker on now
    mov     bx, 600
pause1:
    mov     cx, 65535
pause2: 
    dec     cx
    jne     pause2
    dec     bx
    jne     pause1
    in      al,61h
    and     al,11111100b
    out     61h,al
;end_beep:
 
 
    mov     cx,2500                 ;2nd beep tone frequencybeep1:
       ; call    beep                    ;go sound the beep
 
;beep:
    mov     al,10110110b                    ;load control word
    out     43h,al                          ;send it
    mov     ax,cx                           ;tone frequency into AX
    out     42h,al                          ;send LSB
    mov     al,ah                           ;move MSB to AL
    out     42h,al                          ;send it
    in      al,61h                          ;get port 61 state
    or      al,00000011b                    ;turn on speaker
    out     61h,al                          ;speaker on now
    mov     bx, 600
pause3:
    mov     cx, 65535
pause4: 
    dec     cx
    jne     pause4
    dec     bx
    jne     pause3
    in      al,61h
    and     al,11111100b
    out     61h,al
;end_beep:
 
 
    ;jmp     end_beep                ;we're done
pop cx
pop bx
pop ax          ;retrieves (pops) content of register ax from stack
pop dx          ;retrieves (pops) content of register dx from stack
popf
 
IRET
 
ToBeExec Endp
 
 
start:
 
 
init_intctrl:
    mov     al,11h
    out     MASTR0,al
    mov     al,8
    out     MASTR1,al
    mov     al,4   
    out     MASTR1,al
    mov     al,1
    out     MASTR1,al
    mov     al,11h
    out     SLAVE0,al
    mov     al,70h
    out     SLAVE1,al
    mov     al,2
    out     SLAVE1,al
    mov     al,1
    out     SLAVE1,al
 
 
;Install the new interrupt vector 72h
mov ax, cs              ; get the code segment
mov ds, ax
mov dx, offset ToBeExec
mov ah, 25h             ; sets the interrupt vector
            ; DS:DX holds the address of the new interrupt procedure
mov al, 72h             ; defines the interrupt
int 21h
 
 
mov dx,00a0h            ; this number indicates how many "paragraphs" 
            ; of 16 bytes each will be reserved in memory 
            ; for the TSR program
mov ax, 3100h           ; Program Terminates and Stays Resident in memory 
int 21h
 
mov     ax,4c00h
int     21h
 
END     main