汇编改成C

只看该作者 · 2009-1-11 09:34

                  MOV        A,#43H
        MOV        DPTR,#0000H
        MOVX    @DPTR,A
        INC        DPTR

这个改成C语言怎样改呢？

是不是这样：
uchar  xdata stdata _at_ 0x0000;//定义变量

程序段中：

stdata = 0x43;//赋值
请指点

2万 · 2009-1-11 09:52

sfr16 DPTR     = 0x82;
XBYTE[0x0000] = 0x43;
DPTR ++;

反汇编:
C:0x0275    900000   MOV      DPTR,#C_STARTUP(0x0000)
C:0x0278    7443     MOV      A,#0x43
C:0x027A    F0       MOVX     @DPTR,A
   450:         DPTR ++;
   451:
C:0x027B    0582     INC      DPTR(0x82);//inc dpl
C:0x027D    E582     MOV      A,DPTR(0x82)
C:0x027F    7002     JNZ      C:0283
C:0x0281    0583     INC      DPH(0x83)

一般为：
unsigned char i;
xdata unsigned char buff[200];
    for (i = 0;i < sizeof(buff); i ++)
    {
        buff = 0x43;
    }
反汇编:
   439: unsigned char i;
   440: xdata unsigned char buff[200];
   441:         for (i = 0;i < sizeof(buff); i ++)
   442:         {
   443:                 buff = 0x43;
C:0x0259    7FC8     MOV      R7,#T2CON(0xC8);//200
C:0x025B    900000   MOV      DPTR,#C_STARTUP(0x0000)
C:0x025E    7443     MOV      A,#0x43
C:0x0260    F0       MOVX     @DPTR,A
C:0x0261    A3       INC      DPTR
C:0x0262    DFFC     DJNZ     R7,C:0260
   444:         }

2万 · 2009-1-11 10:10

unsigned char i;
extern unsigned char xdata buff[200] _at_ 0x8000;
    for (i = 0;i < sizeof(buff); i ++)
    {
        buff[0x2000 + i] = 0x43;
    }
实际还是：
unsigned char i;
extern unsigned char xdata buff[200] _at_ 0x0000;
    for (i = 0;i < sizeof(buff); i ++)
    {
        buff[0x2000 + i] = 0x43;
    }

反汇编：
   439: unsigned char i;
   440: extern unsigned char xdata buff[200] _at_ 0x8000;
   441:         for (i = 0;i < sizeof(buff); i ++)
   442:         {
   443:                 buff[0x2000 + i] = 0x43;
C:0x0259    7FC8     MOV      R7,#T2CON(0xC8)
C:0x025B    902000   MOV      DPTR,#0x2000
C:0x025E    7443     MOV      A,#0x43
C:0x0260    F0       MOVX     @DPTR,A
C:0x0261    A3       INC      DPTR
C:0x0262    DFFC     DJNZ     R7,C:0260
   444:         }

所以xdata不需绝对定位，只需：
unsigned char xdata buff[200]；即可

buff[0x2000 + i] = 0x43;

它指出了开始地址0x2000