WindO/I-NV4 User’s Manual 3-75
5 User Communication
3
Communication
â– Conversion Type
After calculating the data using the specified calculation type, select the type of conversion for the data from the
following.
â– 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
Hexadecimal 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
Hexadecimal to ASCII
0
(30h)
Data
4
(34h)
0004h
No conversion
00h
Data
04h