5 User Communication
3-74 WindO/I-NV4 User’s Manual
BCC (Block Check Code)
The BCC comparison data is automatically calculated from the receive data and compared with the BCC part of the
receive data.
This can be configured only when RXD is selected as Type on the Command Settings dialog box, and BCC is selected
under Type on the Data Settings dialog box.
â– Calculation Start Position
Specify the position (1 to 15) in the receive data where BCC calculation starts. The position is counted backwards,
with the first position of the receive data taken as 1.
â– Calculation End Position
Specify the position (0 to 15) in the receive data where BCC calculation ends. The position is counted forwards, with
the data position before the BCC taken as 0.
â– Calculation Type
Select the method to calculate the data between the Calculation Start Position and Calculation End Position.
1
(31h)
4
(34h)
5
(35h)
2
(32h)
STX
(02h)
3
(33h)
BCC CR
(0Dh)
(1) (2) (3) (4) (5) (6)
Calculation Start Position:
Receive data:
1
(31h)
4
(34h)
5
(35h)
2
(32h)
STX
(02h)
3
(33h)
BCC CR
(0Dh)
(5) (4) (3) (2) (1) (0)
Calculation End Position:
Receive data:
XOR: Calculates the data with exclusive logical add.
ADD: Calculates the data using addition.
ADD (2's Complement): Calculates the data using addition, inverts the bit and adds one.
Modbus ASCII (LCR): Calculation is performed according to the following procedure. Conversion Type:
Hexadecimal to ASCII, Number of bytes: 2
1. Convert the ASCII characters between Calculation Start Position and Calculation End
Position into 1-byte hexadecimal data for each set of two characters.
Example: 37h, 35h → 75h
2. Calculate the sum of the data obtained in step 1.
3. Invert the bit of the result of step 2 and add one. (2’s complement)
4. Convert the lower one byte data of the result of step 3 into ASCII characters.
Example: 75h → 37h, 35h
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