求助求助！call 为什么转不过去？~~~~~~~~

extrn atoi:far
public exit

data segment   public    'data1'
     i dw 20h
     ;j dw 20h
data ends

stack segment para stack
db 20h dup(0)
stack ends

code segment
   assume cs:code,ss:stack,ds:data
   start:mov ax,data
         mov ds,ax
     call atoi
    ; mov ax,m
    ;mov i,ax
    ;jmp input
   exit: ;mov ax,i
     ;mov k,ax
     mov ah,4ch
     int 21h
code ends
     end start

        

;extrn exit

data segment  public 'data1'
m dw ?
data ends

stack segment para stack
db 20 dup(0)
stack ends

code segment
    assume cs:code,ss:stack,ds:data
atoi proc far
     mov ax,data
     mov ds,ax

 lop:mov ah,01h
     int 21h
     cmp al,0dh
     jz next
     xor bx,bx
     and al,0fh
     mov bl,al
     mov ax,m
     mov cx,10
     mul cx
     add ax,bx
     mov m,ax
     jmp lop
next:ret
     atoi endp
code ends
     end