Delta Electronics VFD-S manual Unsigned char* data Å a pointer to the message buffer

Chapter 5 ParametersVFD-S Series

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 Å a pointer to the message buffer

Unsigned char length Å 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:

Content	Address	Functions
AC drive	ggnnH	gg means parameter group, nn means parameter number, for
Parameters		example, the address of Pr 4-01 is 0401H. Refer to chapter 5 for
		the function of each parameter. When reading parameter by
		command code 03H, only one parameter can be read at one
		time.

5-70 Revision August 2008, SE09, SW V2.61