试图让程序循环8086

Question

我在这里有一个程序，它应该在调用中断时循环回来，基本上当我们的8086培训板上按下一个键时。当它运行时，按下一个键并且值显示在屏幕上，但它应该仍在运行，就像按下另一个键一样，屏幕将显示该键。我无法弄清楚为什么在调用硬件中断时它不会循环回来。有什么帮助吗？

BITS 16
CPU 8086
cli


section CONSTSEG USE16 ALIGN=16 CLASS=CONST 
TABLE:  DB "01231xxx45672xxx89AB3xxxCDEF4"  
LETTER: DB '0'
fletter:DB 'F'
clear:  DB "                    "
        DB "                    "
        DB "                    "
        DB "                    "
LEN1:   equ $ - clear

section PROGRAM USE16 ALIGN=16 CLASS=CODE

..start

    MOV AX, 0                   ; 0 for writing to entire screen
    MOV BX, clear               ; pointer to the string in memory
    MOV CX, LEN1                ; number of characters
    MOV DX, 0                   
    MOV SI, DS
    INT 0X10

    ;; sets up the 8259A
    mov DX, 0XFFF4
    mov AL, 00010011b                   ;ICW1
    out DX, AL
    mov DX, 0XFFF6
    mov AL, 00001000b                   ;ICW2
    out DX, AL
    mov AL, 00000001b                   ;ICW4
    out DX, AL
    mov AL, 11111101b                   ;OCW1
    out DX, AL


    ;; Setup the keyboard
    mov DX, 0XFFF2
    mov AL, 00111001b           ; 39H clk 100kHz
    out DX, AL
    mov AL, 00000001b           ; mode: Decoded scan mode, n-key rollover, 8 8-bit display left-entry
    out DX, AL
    mov AL, 11011111b           ; clear FIFO and display
    out DX, AL


    mov AL,01000000B        ;initialize 8279 for read FIFO
    OUT DX,AL   




    mov CX, word 0                      ;  set extra segment to zero
    mov ES, CX                      
    mov [ES:36], word key_isr           ; store the isr in the vector taBLe
    mov [ES:38], CS 


    STI
    jmp $

key_isr:
    mov DX, 1111111111110010B           ;FFF2 into DX "Command"
    IN  AL,DX
    AND AL,00000111B              ;;Ands the register with a mask to see the number of timES a key was prESsed.

    MOV AX, 0                   ; 0 for writing to entire screen
    MOV BX, clear               ; pointer to the string in memory
    MOV CX, LEN1                ; number of characters
    MOV DX, 0                   
    MOV SI, DS
    INT 0X10

    mov DX, 1111111111110000B   ;ADDRESS FOR DATA
    IN  AL, DX
    AND AL, 00111111B           ; masks control and shift bits to see what was prESsed 


    mov BL, AL                  ;For last row
    and BL, 00000100B           ;and with 0X0004H

    jz overhere
    jnz fprint



overhere:
    mov DX, 1111111111001100B       ;LED AdrESs debugging
    out DX, AL                      


    ; bits going to led for debugging
    MOV BX, TABLE
    XLAT                            ;RETURN THE LETTER FROM THE TABLE rESults in AL

    ;Print
    MOV [LETTER], AL

    MOV AX, 0
    MOV BX, LETTER
    MOV CX, 1                       ;length ALways 1
    MOV DX, 0                       ; offset
    MOV SI, DS
    INT 0X10
    jmp end_stuff


fprint:
    mov DX, 1111111111001100B       ;0XFFCC
    out DX, AL
    MOV BX, TABLE
    XLAT



    mov [LETTER], AL
    MOV AX, 1
    MOV BX, fletter
    MOV CX, 1
    MOV DX, 0
    MOV SI, DS
    INT 0X10

    MOV AX, 1
    MOV BX, LETTER
    MOV CX, 1
    MOV DX, 1
    MOV SI, DS
    INT 10H

end_stuff:
    mov     DX, 0XFFF4      ; 8259A data
    mov     AL, 00100000b
    out     DX, AL

    mov     DX, 0XFFF6          ;8259A command
    mov     AL, 11101101b       ; unmasked clock interrupt
    out     DX, AL
    iret
    ; Exit the program