摩托罗拉 68000 组装比较数字

Question

我正在编写的程序以一位数字的形式输入，然后是 space，然后是两位数字。该程序会将这两个数字相加，将数字减 7 直到小于 7，并将该数字与星期几相关联。这是我拥有的：

start:  initIO                  * Initialize (required for I/O)
    setEVT          * Error handling routines
*   initF           * For floating point macros only       

    linein  buffer          *reads in values
    cvta2   buffer,#1       *provided macro to convert ascii to num, read first digit only
    move.b  D0,D1           *Store value in D1
    cvta2   buffer+2,#2     *read the next two digits after space
    move.b  D0,D2           *store
    add.b   D1,D2           *add them together (I can probably use just one register here)

麻烦来了：

for:    cmp.w   week, D2 *<<<<< This is saying invalid syntax, I want to see if the number provided is greater than 7, if not branch out to the next section

/麻烦

    ble done
    subq.w  #7,D2        *If num>7, sub 7

done:   

    lineout dmsg

        break                   * Terminate execution
*
*----------------------------------------------------------------------
*       Storage declarations

buffer: dc.b    80
dmsg:   dc.b    'Done',0
week:   dc.b        *If combined value is greater than this, sub 7
*These are the values to check against to get correct reply
sun:    dc.b    
mon:    dc.b    
tues:   dc.b    
weds:   dc.b    
thurs:  dc.b    
fri:    dc.b    
sat:    dc.b    
*These are the responses for the output
sunr:   dc.b    'Sunday',0
monr:   dc.b    'Monday',0
tuesr:  dc.b    'Tueday',0
wedsr:  dc.b    'Wednesday',0
thursr: dc.b    'Thursday',0
frir:   dc.b    'Friday',0
satr:   dc.b    'Saturday',0

        end

当我弄清楚如何进行上面的比较时，会有更多代码，但它是同一种比较，只是使用结果与星期几的值进行比较，以提供正确的响应。

我尝试过使用各种形式的 cmp（cmpa、cmpi。w/l 等），但我似乎找不到一种方法可以比较这两个值。在尝试比较它或类似的东西之前，我是否必须将我标记为 "week" 的值加载到寄存器中？

I/O的例子：

输入：

1 10

输出：

"Wednesday"

如有任何见解，我们将不胜感激。谢谢你的时间。

Answer 1

您正在尝试与不受支持的寻址模式进行比较（在您的示例中，'week' 操作数不是立即值，而是内存地址）。

要将 D2 与 7 进行比较，您可以使用 cmpi（立即比较）：

cmpi.b #7,d2

如果您需要操作数是一个变量，您必须先将其加载到一个寄存器中：

lea week,a0
...
cmp.b (a0),d2

还要确保 cmp 指令中的操作数大小与您的数据大小相匹配

Answer 2

编辑（问题的工作代码，但未优化）：

start:  initIO                  * Initialize (required for I/O)
    setEVT          * Error handling routines
*   initF           * For floating point macros only    

    linein  buffer
    cvta2   buffer,#1   
    move.l  D0,D1
    cvta2   buffer+2,#2
    move.l  D0,D2
    add.l   D1,D2    

    divu.w  #[=10=]07,D2   

    lsr.l   #,D2 *Shift remainder
    lsr.l   #,D2    

    move.w  sun,A2
    cmp.w   A2,D2
    BNE monday
    lineout sunr
    BEQ end

monday: 
    move.w  mon,A2
    cmp.w   A2,D2
    BNE tuesda
    lineout monr
    BEQ end    

tuesda: 
    move.w  tues,A2
    cmp.w   A2,D2
    BNE wednes
    lineout tuesr
    BEQ end    

wednes: 
    move.w  weds,A2
    cmp.w   A2,D2
    BNE thursd
    lineout wedsr
    BEQ end    

thursd: 
    move.w  thurs,A2
    cmp.w   A2,D2
    BNE friday
    lineout thursr
    BEQ end    

friday: 
    move.w  fri,A2
    cmp.w   A2,D2
    BNE saturd
    lineout frir
    BEQ end    

saturd: 
    lineout satr
    BEQ end    

end:    
        break                   * Terminate execution
*
*----------------------------------------------------------------------
*       Storage declarations

buffer: dc.b    80
wkmsg:  dc.w    'The day of the week is '
week:   equ 
sun:    dc.w    
mon:    dc.w    
tues:   dc.w    
weds:   dc.w    
thurs:  dc.w    
fri:    dc.w    
sat:    dc.w    
sunr:   dc.w    'Sunday',0
monr:   dc.w    'Monday',0
tuesr:  dc.w    'Tueday',0
wedsr:  dc.w    'Wednesday',0
thursr: dc.w    'Thursday',0
frir:   dc.w    'Friday',0
satr:   dc.w    'Saturday',0

        end

摩托罗拉 68000 组装比较数字

Motorola 68000 assembly comparing numbers

assembly

conditional

68000

motorola