Sinee EM500 - Page 409

EM500 Open-Loop Vector Control Inverter User Manual
409
unsigned int CRC_Cal_Value(unsigned char *Data, unsigned char Length)
{
unsigned int crc_value = 0xFFFF;
int i = 0;
while(Length--)
{
crc_value ^= *Data++;
for(i=0;i<8;i++)
{
if(crc_value & 0x0001)
{
crc_value = (crc_value>>1)^ 0xa001;
}
else
{
crc_value = crc_value>>1;
}
}
}
return(crc_value);
}
The contents above illustrate CRC parity theory. It takes a long time for execution
with this method, especially when the parity data is long. Therefore, use the following
two loop-up table methods for 16-bit and 8-bit controllers

CRC16 look-up table for 8-bit processor: the finally returned result of this program
is with high byte in the front, so please reverse it while sending)
const Uint8 crc_l_tab[256] = {
0x00,0xC1,0x81,0x40,0x01,0xC0,0x80,0x41,0x01,0xC0,0x80,0x41,0x00,0xC1,0x81,0x40,
0x01,0xC0,0x80,0x41,0x00,0xC1,0x81,0x40,0x00,0xC1,0x81,0x40,0x01,0xC0,0x80,0x41,