CPU 8086

chunksize equ 0x20
devicedelay equ 0x08

_start:
    push bp
    mov bp, sp
    sub sp, 8
    mov [bp-2], word chunksize ; recv size
    mov [bp-4], word 0xf000 ; recv addr
    mov [bp-6], word 0x0001 ; send size
    mov [bp-8], word 0x7000 ; send addr
    mov bx, [bp-8]
    mov [bx], byte 0x42
l0:
    cmp word [bp-4], 0xf600
    jb l1
l2:
    mov sp, bp
    pop bp
    ret
l1:
    mov ah, 0x07
    int 0x80
    test al, al
    jnz l1
    push word [bp-2]
    push word [bp-4]
    mov ah, 0x05
    int 0x80
    test al, al
    jz l2
    mov ah, 0
    add [bp-4], ax
    push word [bp-6]
    push word [bp-8]
    mov ah, 0x06
    int 0x80
    add sp, 8
    mov cx, devicedelay
l3: 
    mov ah, 0x07
    push cx
    int 0x80
    pop cx
    loop l3             ; give the device some time to answer
    jmp l0