modbus 主站源程程序
unsigned cal_crc( char * pucFrame, char usLen )
int readDO(unsigned wReg, unsigned *pwValue)
int readDI(unsigned wReg, unsigned *pwValue)
int readAO(unsigned wReg, unsigned *pwValue)
int readAI(unsigned wReg, unsigned *pwValue)
int writeDO(unsigned wReg, unsigned pwValue)