摩托罗拉68000组件比较号

Question

我正在编写的程序以单个数字编号的形式输入，后跟一个空格，后跟一个两位数字。该计划将采用这两个数字并将它们加在一起，将数字减少7s，直到少于7，并将该数字与一周中的某一天相关联。这里是我有：

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) 

这里是麻烦：

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 $7 *If combined value is greater than this, sub 7 
*These are the values to check against to get correct reply 
sun: dc.b $1 
mon: dc.b $2 
tues: dc.b $3 
weds: dc.b $4 
thurs: dc.b $5 
fri: dc.b $6 
sat: dc.b $7 
*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 

将会有更多的代码，当我弄清楚如何使上面的比较，但只是将结果与星期值进行比较才能提供正确的响应。我曾尝试使用各种形式的cmp（cmpa，cmpi.w/l等），但我似乎无法找到允许我比较两个值的方法。在尝试比较它之前，我是否必须将我标记为“星期”的值加载到寄存器中？的I/O

实例：

输入：

输出：

“星期三”

任何洞察力是赞赏。谢谢你的时间。

Answer 1

您试图执行与不支持的寻址模式的比较（在您的示例中，“周”操作数不是立即值，而是存储器地址）。

要使用7比较D2可以使用CMPI（比较立即数）：

cmpi.b #7,d2 

如果你需要的操作数是一个变量，必须将它加载到寄存器中第一：

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

还要确保操作数大小在CMP指令数据的大小相匹配

Answer 2

编辑（工作问题代码需要提醒的是它不优化） ：

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 #$0007,D2 

    lsr.l #$08,D2 *Shift remainder 
    lsr.l #$08,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 $7 
sun: dc.w $1 
mon: dc.w $2 
tues: dc.w $3 
weds: dc.w $4 
thurs: dc.w $5 
fri: dc.w $6 
sat: dc.w $7 
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