#include <reg52.h>
sbit ENLED = P1^4;
sbit ADDR3 = P1^3;
sbit ADDR2 = P1^2;
sbit ADDR1 = P1^1;
sbit ADDR0 = P1^0;
main()
{     unsigned int  n=0;
    while (1)
    {    n++;
    switch (n%6)
        {
            case 0:
                ADDR0 = 0;
                ADDR1 = 0;
                ADDR2 = 0;
                break;
            case 1:
                ADDR0 = 1;
                ADDR1 = 0;
                ADDR2 = 0;
                break;
            case 2:
                ADDR0 = 0;
                ADDR1 = 1;
                ADDR2 = 0;
                break;
            case 3:
                ADDR0 = 1;
                ADDR1 = 1;
                ADDR2 = 0;
                break;
            case 4:
                ADDR0 = 0;
                ADDR1 = 0;
                ADDR2 = 1;
                break;
            case 5:
                ADDR0 = 1;
                ADDR1 = 0;
                ADDR2 = 1;
                break;
        }     } }

就是问：15和16，25和26为何跳过去没执行？程序哪里错了？先谢了。

上面回答不对哦。用keil单步就那样，困惑中...........

问题解决了，是软件设置问题。谢谢大家。