3Com VFD-D D manual Opening door is prohited

Chapter 4 Parameter SettingsDD Series

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;		// return register CRC
Address list
Content	Address			Function
AC drive Parameters	GGnnH	GG means parameter group, nn means parameter number, for
		example, the address of Pr.04-01 is 0401H.
Drive Command	2000H	Bit0~3		0: No function
				1: Stop
				2: Run
				3: opening door is prohited
		Bit4~5		00B: No function
				01B: OD
				10B: CD
				11B: Change direction
		Bit6~7		00B: 1st accel/decel
				01B: 2nd accel/decel
				10B: 3rd accel/decel
				11B: 4th accel/decel
		Bit08~11		000B: master speed
			4-72