请给出修改后的详细代码

由于原始代码片段中并没有包含完整的按键处理逻辑，所以我将假设已经有一个基础的按键检测函数`keyPress()`来处理按键输入，并且结合前面提到的解题思路，我会给出一个大致的代码框架，其中包含了按键模式切换以及时间的显示和调整。注意实际应用中，你可能还需要添加更多的错误检查和边界条件处理。

#include <reg51.h>

#define SET_KEY 0x01  // Set key code (for example, P2.0 or GPIO pin)
#define UP_KEY  0x02  // Up key code
#define DOWN_KEY 0x03  // Down key code

char flag_dis=0, i_dis=0;
unsigned char hour=8, minute=40, second=0, ad_hour=0, ad_minute=0, ad_second=0;
unsigned long ms_sys=0, flag_1000ms=0, flag_2ms=0;
unsigned char mode=0; // Mode variable to track current state (0=show time, 1=adjust hour, etc.)
unsigned char keyState;

void Timer1_Init();
void displayClock_8seg7();
void keyPressDetect();  // Assuming this function is provided to check button inputs
void setHourMode();
void setMinuteMode();
void setSecondMode();

void main()
{
    Timer1_Init();
    EA = 1;
    while(1)
    {
        keyPressDetect(); // Check for button presses
        if(keyState == SET_KEY)
            mode = (mode + 1) % 4;  // Switch modes every SET_KEY press (0-show, 1-hour, 2-minute, 3-second)

        switch(mode)
        {
            case 0:
                // Display regular time
                if(flag_1000ms == 1)
                    second++;
                displayClock_8seg7();
                break;
            case 1:
                setHourMode();
                break;
            case 2:
                setMinuteMode();
                break;
            case 3:
                setSecondMode();
                break;
        }
    }
}

...

void setHourMode()
{
    if(flag_1000ms == 0)  // Only allow modification when in this mode
    {
        if(keyState == UP_KEY)
            ad_hour++;
        else if(keyState == DOWN_KEY)
            ad_hour--;
        if(ad_hour > 23) ad_hour = 0;
        // Store the adjusted value and return to show time mode
        // ad_hour = ... (Save logic here)
        mode = 0;
    }
}

// Similar functions for setMinuteMode() and setSecondMode()

void Timer1_Isr(void) interrupt 3
{
    // ...
}

void keyPressDetect()
{
    // Here you would implement your key detection logic, like checking P2.0, P2.1, and P2.2 pins.
    // For simplicity, let's assume it returns the key pressed as 'keyState'.
    // keyState = keyPressDetect();
    // ...
}

这只是一个基本的框架，具体的按键处理和时间保存细节需要你自己完善，比如如何在各个模式之间保存和恢复时间，以及如何在显示时间内实现闪烁等。