改变1CH号中断显示时钟

改变1CH号中断，显示时钟：

count_val = 18
dpage     = 0
row       = 0
column    = 80-buff_len
color     = 0f4h;07h
code segment
    assume cs:code,ds:code
count dw count_val
hhhh  db ?,?,':'
mmmm  db ?,?,':'
ssss  db ?,?
buff_len = $-offset hhhh
cursor dw ?
new1ch:
    cmp cs:count,0
    jz  next
    dec cs:count
    iret
next:
    mov  cs:count,count_val
    sti
    push ds
    push es
    push ax
    push bx
    push cx
    push dx
    push si
    push bp
    push cs
    pop  ds
    push ds
    pop  es
    call get_t
    mov  bh,dpage
    mov  ah,3
    int  10h
    mov  cursor,dx
    mov  bp,offset hhhh
    mov  bh,dpage
    mov  dh,row
    mov  dl,column
    mov  bl,color
    mov  cx,buff_len
    mov  al,0
    mov  ah,13h
    int  10h
    mov  bh,dpage
    mov  dx,cursor
    mov  ah,2
    int  10h
    pop  bp
    pop  si
    pop  dx
    pop  cx
    pop  bx
    pop  ax
    pop  es
    pop  ds
    iret
get_t proc
    mov ah,2
    int 1ah
    mov al,ch
    call ttasc
    xchg ah,al
    mov word ptr hhhh,ax
    mov al,cl
    call ttasc
    xchg ah,al
    mov word ptr mmmm,ax
    mov al,dh
    call ttasc
    xchg ah,al
    mov word ptr ssss,ax
    ret
get_t endp
ttasc proc
    mov ah,al
    and al,0fh
    shr ah,1
    shr ah,1
    shr ah,1
    shr ah,1
    add ax,3030h
    ret
ttasc endp
old1ch dd ?
start:
    push cs
    pop ds
    mov ax,351ch
    int 21h
    mov word ptr old1ch,bx
    mov word ptr old1ch+2,es
    mov dx,offset new1ch
    mov ax,251ch
    int 21h
    ;...
    mov ah,0
    int 16h
    lds dx,old1ch
    int 21h
    mov ah,4ch
    int 21h
code ends
end start