VFD-B Series
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5-62
Step 3: Examine the LSB of CRC register.
Step 4: If the LSB of CRC register is 0, shift the CRC register one bit to the right with
MSB zerofilling, then repeat step 3. If the LSB of CRC register is 1, shift the
CRC register one bit to the right with MSB zerofilling, Exclusive OR the CRC
register with the polynomial value A001H, then repeat step 3.
Step 5: Repeat step 3 and 4 until eight shifts have been performed. When this is done,
a complete 8-bit byte will have been processed.
Step 6: Repeat step 2 to 5 for the next 8-bit byte of the command message. Continue
doing this until all bytes have been processed. The final contents of the CRC
register are the CRC value. When transmitting the CRC value in the
message, the upper and lower bytes of the CRC value must be swapped,
i.e. the lower order byte will be transmitted first.
The following is an example of CRC generation using C language. The function takes two
arguments:
Unsigned char* data î›… a pointer to the message buffer
Unsigned char length î›… the quantity of bytes in the message buffer
The function returns the CRC value as a type of unsigned integer.
Unsigned int crc_chk(unsigned char* data, unsigned char length){
int j;
unsigned int reg_crc=0xFFFF;
while(length--){
reg_crc ^= *data++;
for(j=0;j<8;j++){
if(reg_crc & 0x01){ /* LSB(b0)=1 */
reg_crc=(reg_crc>>1) ^ 0xA001;
}else{
reg_crc=reg_crc >>1;
}
}
}
return reg_crc;
}
3.5 Address list:
The contents of available addresses are shown as below:
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