INVT Goodrive GD300-19-004G-4, Руководство по эксплуатации

Страница: 215 / 255

Goodrive300-19 series open loop vector inverter special for hosit Communication protocol
-214-
It is added into the frame after calculated by transmitting device. The receiving device recalculates the
CRC of the received frame and compares them with the value in the received CRC field. If the two
CRC values are different, there is an error in the communication.
During CRC, 0xFFFF will be stored. And then, deal with the continuous 6-above bytes in the frame
and the value in the register. Only the 8Bit data in every character is effective to CRC, while the start
bit, the end and the odd and even check bit is ineffective.
Each 8 bit character xors with the register, the result moves to the lowest effective bit and the highest
bit is filled by 0. If LSB is detected to be 1, the register will xor with the preset value. If LSB is 0, the
action will not carry on. Repeat 8 times during the whole process. After the last bit is completed, the
next 8 bit character will xor with the current value of the register. The final value in the register is the
CRC after the completion of operating all bytes.
The calculation of CRC applies the international standard CRC checkout principles. When the user is
editing CRC calculation, he can refer to the relative standard CRC calculation to write the required
CRC calculation program.
Here provided a simple function of CRC calculation for the reference (programmed with C language):
unsigned int crc_cal_value(unsigned char*data_value,unsigned char data_length)
{
int i;
unsigned int crc_value=0xffff;
while(data_length--)
{
crc_value^=*dat+;
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);
}
In ladder logic, CKSM calculated the CRC value according to the frame with the table inquiry. The