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（2VC≈2×5V≈10V2V_C \approx 2 \times 5V \approx 10V2VC≈2×5V≈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 :msSTCISP_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                        0typedef 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                 0x81unsigned 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 communicationelse 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,8HnMS10 = (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 ICWaitTime(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
//------------------------------------------------------------------------------