Toshiba VF-AS1 Series, RS485 CRC Generation, Error codes, Bit counter =, End Return CRC

E6581315

5.2. CRC Generation

“CRC” is a system to check errors in communication frames during data transmission. CRC is composed of two bytes and has hexadecimal-bit binary values. CRC values are generated by the transmission side that adds CRC to messages. The receiving side regenerates CRC of received messages and compares generation results of CRC regeneration with CRC values actually received. If values do not match, data will be aborted.

„Flow

CRC generation ( )

CRC initial data: FFFF

Byte counter n = 0

Nｏ

Byte counter n < Length

Yes

CRC = (CRC XOR nth send byte (0 expanded to word (higher 8 bits))

Bit counter = 0

Bit counter < 8	Nｏ
Yes
C = (Remainder of CRC ÷ 2)
ＣＲＣ >> １
Is remainder (C)	Nｏ
other than 0?
Yes
CRC＝
(CRC XOR generating polyno-
mial (A001))
Bit counter +1

Byte counter +1

A procedure for generating a CRC is:

1, Load a 16–bit register with FFFF hex (all 1’s). Call this the CRC register.

2.Exclusive OR the first 8–bit byte of the message with the low–order byte of the 16–bit CRC register, putting the result in the CRC register.

3.Shift the CRC register one bit to the right (toward the LSB), zero–filling the MSB. Extract and examine the LSB.

4.(If the LSB was 0): Repeat Step 3 (another shift).

(If the LSB was 1): Exclusive OR the CRC register with the polynomial value A001 hex (1010 0000 0000 0001).

5.Repeat Steps 3 and 4 until 8 shifts have been per- formed. When this is done, a complete 8–bit byte will have been processed.

6.Repeat Steps 2 through 5 for the next 8–bit byte of the message. Continue doing this until all bytes have been processed.

7.The final contents of the CRC register is the CRC value.

8.When the CRC is placed into the message, its upper and lower bytes must be swapped as described below.

End (Return CRC)

5.3. Error codes

In case of the following errors, the return commands from the inverters are added 80h to the com- mands received by the inverters. The following error codes are used.

Error Code	Description
01	Command error (Returned when a command other than 03 or 06 is received)

02Communication number error (A communication number is not found when Com- mand 03 or 06 is received)

03	Data range error (Data range error when Command 03 or 06 is received
	Unable to execute (Command 06 is being received and data cannot be written)

04(1) Writing in write-disable-during-operation parameter

(2) Writing in parameter that is executing TYP

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