IDEC High Performance Series - Manual (Page 166)

5 User Communication
3-64 WindO/I-NV2 User’s Manual
■ Conversion Type
After calculating the data using the specified calculation type, select the type of conversion for the data from the
following.
■ Number of bytes
After converting according to the specified conversion type, select 1 or 2 for the number of bytes for comparison
data.
Example: BCC for receive command data
This example describes the case of comparing the BCC calculation result for the following receive data with the BCC
part of the receive data.
• Calculation Start Position and Calculation End Position
When Calculation Start Position is 2 and Calculation End Position is 1: Calculates the range 1234.
• Calculation Type
• Conversion Type
When the BCC calculation result is 0004h, the converted data is as follows.
Modbus RTU (CRC): CRC-16 (Generating polynomial:x 16 +x 15 +x 2 +1) is calculated according to the following
procedure. Conversion Type: No Conversion, Number of bytes: 2
1. Obtain an exclusive OR (XOR) of 1 byte data at Calculation Start Position and FFFFh.
2. If the least significant bit of the result of step 1 is 0, shift to the right by one bit. If the
bit is 1, shift to the right by 1 bit and obtain XOR of the result and the value (A001h).
3. Repeat step 2 to shift 8 times.
4. Obtain XOR of the next one byte of data and the result of step 3.
5. Repeat steps 2 through 4 until the data at Calculation End Position is processed.
6. Compare the result of step 5 in the order of the lower byte and upper byte.
Example: 1234h → 34h, 12h
Binary (HEX) to ASCII: Considers the data as binary-coded hexadecimal number and converts it to ASCII data.
No conversion: No conversion is performed.
XOR: 31h^32h^33h^34h^=04h
ADD: 31h+32h+33h+34h=CAh
ADD (2's Complement): Inverts the bit of CAh+1=36h
Modbus ASCII (LCR): BA→42h, 41h
Modbus RTU (CRC): BA30h→BAh, 30h
1
(31h)
4
(34h)
5
(35h)
2
(32h)
STX
(02h)
3
(33h)
BCC CR
(0Dh)
1
(31h)
4
(34h)
5
(35h)
2
(32h)
STX
(02h)
3
(33h)
BCC CR
(0Dh)
(1) (2) (3) (4) (5) (6) Calculation Start Position:
(5) (4) (3) (2) (1) (0) Calculation End Position:
Data used for BCC calculation
0004h
Binary (HEX) to ASCII
0
(30h)
Data
4
(34h)
0004h
No conversion
00h
Data
04h