使用单片机对STC8G,8H,8A进行ISP下载程序

通过第三方程序实现对STC单片机的程序下载，可以方便进行现场的调试和更新。特别是对于设计远程程序更新、无线程序下载与调试等功能有帮助。

本文给出了下载相关的一些程序设计。

STC单片机ISP下载协议

在手边并没有成文的对STC单片机ISP下载协议，仅仅在STC官方网站的STC8G,8H,8A单片机手册中给出了“使用第三方MCU对STC8G，8H, 8A”系列的但潘辰进行ISP下载的范例程序。参考这些程序，可以完成对STC8G系列的单片机内部的FLASH程序的更新。

^{▲ STC8G技术手册中的下载协议}

对于STC单片机内部的“硬件选项”，手册建议还是使用官方的原来的STC-ISP下载程序完成配置，这比较可靠。

^{▲ STC单片机的硬件选项}

STC的ISP下载程序

下面给出了使用STC8G1K17单片机中，C语言实现的ISP程序。

下面给出单片机借助的外部资源以及相应的源码。

1. UART2

程序使用了STC8G1k的UART2完成对下载MCU发送相关的指令。需要注意的是，在ISP通信过程UART2需要设置为9bit的工作模式，这在开始的我并没有注意，造成前期的调试受阻。

为了避免串口线对被调试单片机反向供电，特别是在外部单片机掉电进行冷启动的过程中，由于串口的电压可能仍然能够满足被下载单片机的工作电源需要，通过对UART2对应的输出管脚置为高阻状态来避免反向供电。这一点，并没有像STC8G1K08手册中推荐的使用电阻和二极管来进行电源个的的方案。

^{▲ STC单片机数据手册中推荐的串口电源隔离方案}

2. CCP2

使用了STC8G1K08的CCP2产生PWM波形来整流出高压（ $2V_C \approx 2 \times 5V \approx 10V$）来驱动MOS管。详细的方案可以参见博文如何利用单片机IO口产生两倍的电源电压中的描述。

在对被下载单片机电源控制的同时，也需要改变UART2的RXD，TXD管脚的输出状态。在关闭电源的时候，将RXD,TXD设置为INPUT的高阻模式，可以避免对ISP单片机端口供电。下面代码显示了这里的控制。

//------------------------------------------------------------------------------
void ispPowerOn(void) {
    P10V_ON;
    PM_BIDIR(RXD2_PIN);
    PM_PP(TXD2_PIN);
}

void ispPowerOff(void) {
    PM_INPUT(RXD2_PIN);
    PM_INPUT(TXD2_PIN);
    P10V_OFF;    
}

3. 完整的源码

程序的其它部分可以参见数据手册中的范例程序进行阅读。由于没有正式的问题，在这里也就不再对下载的协议反向解释了。

程序的头文件。

/*
**==============================================================================
** STCISP.H:            -- by Dr. ZhuoQing, 2020-04-30
**
**  Description:
**
**==============================================================================
*/
#ifndef __STCISP__
#define __STCISP__
//------------------------------------------------------------------------------
#ifdef STCISP_GLOBALS
   #define STCISP_EXT
#else
   #define STCISP_EXT extern
#endif // STCISP_GLOBALS
//------------------------------------------------------------------------------
//==============================================================================

#define PWM_PIN                 3, 7
#define P5V_PIN                 3, 6                                                                

#define RXD2_PIN                1, 0
#define TXD2_PIN                1, 1
                                                               
                               
//------------------------------------------------------------------------------
#define P10V_ON                 ON(P5V_PIN), PWM3SetPWM(0x7f)        		
#define P10V_OFF                OFF(P5V_PIN), PWM3SetPWM(0xff)

//------------------------------------------------------------------------------

void ispInit(unsigned long lnBaud);

void ispPowerOn(void);
void ispPowerOff(void);

#define ISP_POWEROFF_TIME      200         // unit :ms

STCISP_EXT unsigned int g_nIspPowerOffTime;

void ispSetBaud(unsigned long lnBaud, unsigned char uc9BitFlag);
                                            // uc9BitFlag: 1 : Set UART2 as 9bit mode
                                            //             0 : as 8 bit mode

//------------------------------------------------------------------------------
STCISP_EXT unsigned int g_nispReceiveSum;
STCISP_EXT unsigned char g_ucispReceiveIndex, g_ucispReceiveCount, g_ucispReceiveStep;
STCISP_EXT unsigned char xdata g_ucispRxBuffer[64], g_ucispTxBuffer[150];
STCISP_EXT unsigned char g_ucispReceiveFlag;

//------------------------------------------------------------------------------
STCISP_EXT unsigned int g_nispProgramStart;
STCISP_EXT unsigned char g_ucispProgramLength;

#define ISP_PROGRAM_BUFFER          256
STCISP_EXT unsigned char xdata g_ucispProgramBuffer[ISP_PROGRAM_BUFFER];

//------------------------------------------------------------------------------

void ispProcChar(void);
void ispCommunicationInit(void);
unsigned char ispSendChar(unsigned char ucChar);
void ispCommandSend(unsigned char ucSize);
void ispRun(unsigned long lnBaud, unsigned int nTime);


//------------------------------------------------------------------------------
void ispShowRxBuffer(void);

//------------------------------------------------------------------------------
#define FALSE                       1
#define TRUE                        0

typedef bit                         BOOL;
typedef unsigned char               BYTE;
typedef unsigned short              WORD;

#define LOBYTE(w)                   ((BYTE)(WORD)(w))
#define HIBYTE(w)                   ((BYTE)((WORD)(w) >> 8))


#define FUSER                       35000000L
#define RL(n)                       (0x10000 - FUSER/4/(n))

#define ISP_DOWNLOAD_CHECKLOOP      100
#define ISP_DOWNLOAD_BAUD           115200L
#define ISP_DOWNLOAD_TIMEOUT        2000
#define ISP_DOWNLOAD_TIMEOUT_ERASE  2000
#define ISP_DOWNLOAD_PAGESIZE       128


//------------------------------------------------------------------------------
#define ISP_ARG7_8H                 0x97
#define ISP_ARG7_8G                 0x97
#define ISP_ARG7_8A                 0x81

unsigned char ispEnterISP(unsigned long lnStartBaud, unsigned long lnBaud, 
                          unsigned char ucArg7, unsigned long lnFosc);
                          
unsigned char ispEraseMCU(void);
unsigned char ispDownloadCode(unsigned char * pucCode, unsigned int nSize, 
                              unsigned int nStartAddress);

//------------------------------------------------------------------------------





//==============================================================================
//             END OF THE FILE : STCISP.H
//------------------------------------------------------------------------------
#endif // __STCISP__

程序的C语言文件。

/*
**==============================================================================
** STCISP.C:             -- by Dr. ZhuoQing, 2020-04-30
**
**==============================================================================
*/

//------------------------------------------------------------------------------
#define STCISP_GLOBALS        1              // Define the global variables
#include "STCISP.H"
#include "STC8G.H"
#include "C51BASIC.H"
#include <STDIO.H>

//------------------------------------------------------------------------------

void ispInit(unsigned long lnBaud) {
    //--------------------------------------------------------------------------    
    ispSetBaud(lnBaud, 0);
    
    //--------------------------------------------------------------------------
    ispCommunicationInit();

    //--------------------------------------------------------------------------
    
    PM_PP(PWM_PIN);
    PM_PP(P5V_PIN);

    P10V_ON;  
    
    g_nIspPowerOffTime = ISP_POWEROFF_TIME;
    
}

//------------------------------------------------------------------------------
void ispRun(unsigned long lnBaud, unsigned int nTime) {
    ispPowerOff();
    WaitTime(nTime);
    ispPowerOn();
    
    ispSetBaud(lnBaud, 0);
    UART2_CLEAR;
}


//------------------------------------------------------------------------------
void ispPowerOn(void) {
    P10V_ON;
    PM_BIDIR(RXD2_PIN);
    PM_PP(TXD2_PIN);
}

void ispPowerOff(void) {
    PM_INPUT(RXD2_PIN);
    PM_INPUT(TXD2_PIN);
    P10V_OFF;    
}

void ispSetBaud(unsigned long lnBaud, unsigned char uc9BitFlag) {
    unsigned int nNumber;
    nNumber = Baud2TimeReload(lnBaud, 35000000L);

    if(uc9BitFlag)    
        S2CON |= 0x80;                          // Enable bit9 communication
    else S2CON &= ~0x80;
    
    
    T2H = nNumber >> 8;
    T2L = nNumber;
}

void ispCommunicationInit(void) {
    unsigned int i;
    
    for(i = 0; i < sizeof(g_ucispRxBuffer); i ++)
        g_ucispRxBuffer[i] = 0;
        
    g_nispReceiveSum = 0;
    g_ucispReceiveIndex = g_ucispReceiveCount = g_ucispReceiveStep = 0;
    g_ucispReceiveFlag = 0;
    
}


//------------------------------------------------------------------------------
void ispProcChar(void) {
    unsigned char ucChar;
    
    if(!UART2_CANRECE) return;    
    UART2ReceChar(&ucChar);
    
    //--------------------------------------------------------------------------
//    printf("%bx ", ucChar);
    
    //------------------------------------------------------------------------        
    switch(g_ucispReceiveStep) {
        case 1:
            if(ucChar != 0xb9) goto L_CheckFirst;
            g_ucispReceiveStep ++;
            break;
           
        case 2:
            if(ucChar != 0x68) goto L_CheckFirst;
            g_ucispReceiveStep ++;
            break;
        
        case 3:
            if(ucChar != 0x0) goto L_CheckFirst;
            g_ucispReceiveStep ++;
            break;
            
        case 4:
            g_nispReceiveSum = 0x68 + ucChar;
            g_ucispReceiveCount = ucChar - 6;
            g_ucispReceiveIndex = 0;
            g_ucispReceiveStep ++;
            break;
            
        case 5:
            g_nispReceiveSum += ucChar;
            g_ucispRxBuffer[g_ucispReceiveIndex ++] = ucChar;
            if(g_ucispReceiveIndex == g_ucispReceiveCount)
                g_ucispReceiveStep ++;
            break;
            
        case 6:
            if(ucChar != (unsigned char)(g_nispReceiveSum >> 8))
                goto L_CheckFirst;
            g_ucispReceiveStep ++;
            break;
        
        case 7:
            if(ucChar != (unsigned char)(g_nispReceiveSum & 0xff))
                goto L_CheckFirst;
            g_ucispReceiveStep ++;
            break;
            
        case 8:
            if(ucChar != 0x16) goto L_CheckFirst;
            g_ucispReceiveFlag = 1;
            g_ucispReceiveStep ++;
            break;
            
L_CheckFirst:
        case 0:
        default:
            ispCommunicationInit();
            if(ucChar == 0x46) g_ucispReceiveStep = 1;
            else g_ucispReceiveStep = 0;
            
            break;
    }
}

//------------------------------------------------------------------------------
/*
void ispShowRxBuffer(void) {
    unsigned int i;
    
    printf("Count:%bd\r\n", g_ucispReceiveCount);
    for(i = 0; i < g_ucispReceiveCount; i ++) 
        printf("%bx ", g_ucispRxBuffer[i]);
    
    printf("\r\n");
}
*/

//------------------------------------------------------------------------------
unsigned char ispSendChar(unsigned char ucChar) {
    g_ucUART2IntFlag = 0;
    
    ACC = ucChar;
    
    S2CON &= ~0x8;
    if(P) S2CON |= 0x8;
    
    S2BUF = ACC;
    
    while(1) {
        if(g_ucUART2IntFlag) break;
    }
    
    return ucChar;    
}


//------------------------------------------------------------------------------
void ispCommandSend(unsigned char ucSize) {
    unsigned int nSum;
    unsigned char i, c;
        
    ispSendChar(0x46);
    ispSendChar(0xb9);
    ispSendChar(0x6a);
    ispSendChar(0x00);
    
    nSum = ucSize + 6 + 0x6a;
    ispSendChar(ucSize + 6);
    
    for(i = 0; i < ucSize; i ++) {
        c = g_ucispTxBuffer[i];
        nSum += c;
        ispSendChar(c);
    }
    
    ispSendChar((unsigned char)(nSum >> 8));
    ispSendChar((unsigned char)(nSum & 0xff));
    ispSendChar(0x16);
    
    
    ispCommunicationInit();
    
}

//------------------------------------------------------------------------------
unsigned char ispEnterISP(unsigned long lnStartBaud, unsigned long lnBaud, 
                          unsigned char ucArg7, unsigned long lnFosc) {
    unsigned char ucArg;
    unsigned int nCheckLoop;
    unsigned int nMS10;
    unsigned int nBaudTimeReload;
    
    
    //----------------------------------------------------------------------            
    ispCommunicationInit();
    ispSetBaud(lnStartBaud, 1);
    
//    printf("Set baud:%ld\r\n", lnStartBaud);
    
    //--------------------------------------------------------------------------
    ispPowerOff();
    WaitTime(g_nIspPowerOffTime);
    ispPowerOn();
    
    
    nMS10 = (unsigned int)(GetClickMS() + 10);
    nCheckLoop = 0;
    
    for(nCheckLoop = 0; nCheckLoop < ISP_DOWNLOAD_CHECKLOOP;) {
        ispProcChar();        
        if(g_ucispReceiveStep == 0) {
            if(GetClickMS() == nMS10) {
                ispSendChar(0x7f);
                nMS10 = (unsigned int)(GetClickMS() + 10);
                nCheckLoop ++;
            }           
        }
        
        if(g_ucispReceiveFlag) {
            ucArg = g_ucispRxBuffer[4];
            if(g_ucispRxBuffer[0] == 0x50)
                break;
            
            return 1;                       // return error 
        }
        

    }
    
    
    if(nCheckLoop >= ISP_DOWNLOAD_CHECKLOOP) return 2;
    
    //--------------------------------------------------------------------------
    // Set new baud
//    printf("\r\nSet new Buad:%ld/%d\r\n", lnBaud, nCheckLoop);
    
    nBaudTimeReload = Baud2TimeReload(lnBaud, lnFosc);
//    printf("%x\r\n", nBaudTimeReload);
    
    
    ucArg = g_ucispRxBuffer[4];
    g_ucispTxBuffer[0] = 0x01;
    g_ucispTxBuffer[1] = ucArg;
    g_ucispTxBuffer[2] = 0x40;
    g_ucispTxBuffer[3] = HIBYTE(nBaudTimeReload);
    g_ucispTxBuffer[4] = LOBYTE(nBaudTimeReload);
    g_ucispTxBuffer[5] = 0x00;
    g_ucispTxBuffer[6] = 0x00;
    g_ucispTxBuffer[7] = ucArg7;//0x97;//0x81;//0x97;                // 0x81: STC8A
                                                            // 0x97: STC8G,8H

    nMS10 = (unsigned int)(GetClickMS() + ISP_DOWNLOAD_TIMEOUT);
    ispCommandSend(8);
    
    for(;;) {
        ispProcChar();
        if(g_ucispReceiveFlag) {
            if(g_ucispRxBuffer[0] == 0x01) break;
            return 3;
        }
        
        if(GetClickMS() == nMS10) return 4;
        
    }
    

    //----------------------------------------------------------------------
    // Prepare the new download baud    
    ispSetBaud(lnBaud, 1);
    
//    WaitTime(10);
    
    g_ucispTxBuffer[0] = 0x05;
    g_ucispTxBuffer[1] = 0x00;
    g_ucispTxBuffer[2] = 0x00;
    g_ucispTxBuffer[3] = 0x5a;
    g_ucispTxBuffer[4] = 0xa5;
        
    nMS10 = (unsigned int)(GetClickMS() + ISP_DOWNLOAD_TIMEOUT);
    ispCommandSend(5);
    for(;;) {
        ispProcChar();
        
        if(g_ucispReceiveFlag) {
            if(g_ucispRxBuffer[0] == 0x05) break;
            return 5;
        }
        
        if(GetClickMS() == nMS10) return 6;

    }
    

    return 0;

}

//------------------------------------------------------------------------------
unsigned char ispEraseMCU(void) {
    unsigned int nMS10;
    
    //----------------------------------------------------------------------    
    // Erase the IC
    WaitTime(10);
    
    g_ucispTxBuffer[0] = 0x03;
    g_ucispTxBuffer[1] = 0x00;
    g_ucispTxBuffer[2] = 0x00;
    g_ucispTxBuffer[3] = 0x5a;
    g_ucispTxBuffer[4] = 0xa5;
    
    
    nMS10 = (unsigned int)(GetClickMS() + ISP_DOWNLOAD_TIMEOUT_ERASE);
    ispCommandSend(5);
    
    for(;;) {
        ispProcChar();
        
        if(g_ucispReceiveFlag) {
            if(g_ucispRxBuffer[0] == 0x03) break;
            return 1;
        }

        if(GetClickMS() == nMS10) return 2;
    }
    
    
    return 0;                               // OK

}

//------------------------------------------------------------------------------s
unsigned char ispDownloadCode(unsigned char * pucCode, unsigned int nSize, unsigned int nStartAddress) {
    unsigned int i, nStep, nLength, j;
    unsigned int nDownloadAddress, nStart, nEnd, nOffset;
    unsigned int nPoint;
    unsigned int nMS10;
    
    
    nStep = (int)((nSize + ISP_DOWNLOAD_PAGESIZE - 1) / ISP_DOWNLOAD_PAGESIZE);
    
    g_ucispTxBuffer[0] = 0x22;
    g_ucispTxBuffer[3] = 0x5a;
    g_ucispTxBuffer[4] = 0xa5;
    
    nOffset = 5;
    nPoint = 0;
    
    for(i = 0; i < nStep; i ++) {
        nStart = i * ISP_DOWNLOAD_PAGESIZE;
        nEnd = nStart + ISP_DOWNLOAD_PAGESIZE;
        if(nEnd > nSize) nEnd = nSize;
        nLength = nEnd - nStart;
        
        nDownloadAddress = nStartAddress + nStart;
        g_ucispTxBuffer[1] = HIBYTE(nDownloadAddress);
        g_ucispTxBuffer[2] = LOBYTE(nDownloadAddress);
        
        for(j = 0; j < nLength; j ++) {
            g_ucispTxBuffer[nOffset + j] = *(pucCode + nPoint);
            nPoint ++;        
        }
        
        nMS10 = (unsigned int)(GetClickMS() + ISP_DOWNLOAD_TIMEOUT);
        
        ispCommandSend(nLength + nOffset);
        
        
        for(;;) {
            ispProcChar();
            
            if(g_ucispReceiveFlag) {
                if(g_ucispRxBuffer[0] == 0x2 &&
                   g_ucispRxBuffer[1] == 'T') break;
                   
                return 1;                   
            }
            if(GetClickMS() == nMS10) return 2;
        }
        
        g_ucispTxBuffer[0] = 0x02;
        
    }
    
    return 0;

}


//==============================================================================
//                END OF THE FILE : STCISP.C
//------------------------------------------------------------------------------