自己用C语言写单片机PIC18 serial bootloader

    for(;;)        //loop until end of file
{
        while (RCREG!=':');        //wait for start of hex file line
        while(!TXSTAbits.TRMT);
        TXREG=':';      //the prompt to download a new program

        cksum = bcount = g2x();        //get the byte count
#if _EEPROMSIZE > 256
        EEADRH = TBLPTRH = g2x();        //get the address
#else
        TBLPTRH =g2x();
#endif
        TBLPTRL = EEADR =g2x();
        DO_NOT_INCREMENT = 1;
        rectype = g2x();    //get the record type
        switch(rectype)
        {
        case DATA:    //ldata record
            #if (PROG_START > 0x200) || defined(__PIC18FX520)    
//to protect bootloader from being overwritten
            if( (FLASH) && (TBLPTRU==0) && (TBLPTRH < (unsigned char)(PROG_START>>8)) )    
//to protect bootloader from being overwritten
                break;        //if bootloader is threatened, skip this
            #endif
        clear_buffer();
            while(bcount--)
            {
                TABLAT = EEDATA = buff[(EEADR&(_FLASH_WRITE_SIZE-1))] = g2x();     //get the data
                if((CONFIG)||(EEPROM))
                {
                    if(CONFIG) //EEPROM/config. write byte at a time
{
                        table_write();
                    }
                    //zap();
}
                else
                {
                    if((EEADR & (_FLASH_WRITE_SIZE-1)) == (_FLASH_WRITE_SIZE-1))  //program/IDLOCs flash bytes at a time
{
                        flash8();
                        clear_buffer();
                    }
                }
                EEADR++;
            }
            if(((EEADR&(_FLASH_WRITE_SIZE-1))!=0)&&(FLASH)&&(!CONFIG))
                flash8();
            checksum();
            break;
        case END:    //end of hex file
checksum();
            TXSTA = 0x02;     //reset USART before jump to application
            RCSTA = 0x00;
            (*((void(*)(void))PROG_START))(); //jump to new program
            break;
        case EXTEND_ADDRESS:    //extended address record
            while(bcount--)
            {
                EEADR=g2x();    //determines whether EE, Config or ID 
}
            EEPGD=1;
            if(EEADR==0xF0)
                EEPGD=0;    //select for EEPROM
            CFGS=0;
            if((EEADR&0xF0)==0x30)
                CFGS=1;        //select for config write
            TBLPTRU=EEADR;
            checksum();
            break;
        }
    }

for(;;)
    {
        while (RCREG != ':');
        while(!TXSTAbits.TRMT);
        TXREG=':';    //the prompt to download a new program

        cksum = bcount =g2x();
        data_buffer[LEN_INDEX] =bcount;
        data_buffer[ADDRH_INDEX] =g2x();
        data_buffer[ADDRL_INDEX] =g2x();
        rectype =g2x();
        switch(rectype)
        {
            caseDATA:
                while (bcount--)
                {
                    data_buffer[LEN_INDEX + data_index + 1] =g2x();
                    data_index++;
                }
                checksum();
                EECON1 =PGM_WRITE;
                WriteMem();
                break;
            caseEND:
                checksum();
                if(block_start)
                {
                    WriteStart();
                    resetBlockBuffer();
                    block_start = 0;
                }
                TXSTA = 0x02; //reset USART before jump to application
                RCSTA = 0x00;
                asm("goto "___mkstr(APP_START));
                break;
            caseEXTEND_ADDRESS:
                g2x();
                data_buffer[ADDRU_INDEX] =g2x();
                checksum();
                break;
        }
        data_index = 0;
    }