3-6
ENGLISH
Description
MODBUS protocol manual
unsigned short ModBus_CRC16( unsigned char * Buffer, unsigned short Length )
{
unsigned char CRCHi = 0xFF;
unsigned char CRCLo = 0xFF;
int Index;
unsigned short ret;
while( Length-- )
{
Index = CRCLo ^ *Buffer++ ;
CRCLo = CRCHi ^ CRC_Table_Hi[Index];
CRCHi = CRC_Table_Lo[Index];
}
ret=((unsigned short)CRCHi << 8);
ret|= (unsigned short)CRCLo;
return ret;
}
OR CAN BE USED CALCULATED METHOD WITHOUT TABLE
/* ModBus_CRC16 Calculatd CRC16 with polynome 0xA001 and init value 0xFFFF
Input *Buffer - pointer on data
Input Lenght - number byte in buffer
Output - calculated CRC16
*/
/*
cur_crc=0xFFFF;
do
{
unsigned int i = 8;
cur_crc = cur_crc ^ *Buffer++;
do
{
if (0x0001 & cur_crc)
{
cur_crc >>= 1;
cur_crc ^= 0xA001;
}
else
{
cur_crc >>= 1;
}
}
while (--i);
}
while (--Length);
return cur_crc;
*/