10: U
SER
C
OMMUNICATION
I
NSTRUCTIONS
10-10
FC5A M
ICRO
S
MART
U
SER
’
S
M
ANUAL
FC9Y-B1268
BCC (Block Check Character)
Block check characters can be appended to the transmit data. The start position for the BCC calculation can be selected
from the first byte through the 15th byte. The BCC can be 1 or 2 digits.
STX
BCC calculation start position can be selected from this range.
1st
“A”
2nd
“B”
3rd
“C”
4th
“D”
5th
“E”
6th
“0”
15th
CR
16th
LF
17th
BCC
18th
BCC
19th
BCC calculation range when starting with the 1st byte of the data.
BCC
(2 digits)
BCC Calculation Start Position
The start position for the BCC calculation can be specified from the first byte through the 15th byte. The BCC is calculated
for the range starting at the designated position up to the byte immediately before the BCC of the transmit data.
Example:
Transmit data consists of 17 bytes plus 2 BCC digits.
(1) Calculation start position = 1
STX
BCC calculation range
1st
“A”
2nd
“B”
3rd
“C”
4th
“D”
5th
“E”
6th
“0”
15th
CR
16th
LF
17th
BCC
18th
BCC
19th
BCC
(2 digits)
(2) Calculation start position = 2
STX
BCC calculation range
1st
“A”
2nd
“B”
3rd
“C”
4th
“D”
5th
“E”
6th
“0”
15th
CR
16th
LF
17th
BCC
18th
BCC
19th
BCC
(2 digits)
BCC Calculation Formula
BCC calculation formula can be selected from XOR (exclusive OR), ADD (addition), ADD-2comp, Modbus ASCII, or Modbus
RTU.
Example:
Conversion results of transmit data consist of 41h, 42h, 43h, and 44h.
“A”
(41h)
“B”
(42h)
“C”
(43h)
“D”
(44h)
ASCII data
(1) BCC calculation formula = XOR
Calculation result = 41h
42h
43h
44h = 04h
(2) BCC calculation formula = ADD
Calculation result = 41h
42h
43h
44h = 10Ah
0Ah (Only the last 1 or 2 digits are used as BCC.)
(3) BCC calculation formula = ADD-2comp
Calculation result = FEh, F6h (2 digits without conversion)
(4) BCC calculation formula = Modbus ASCII
Calculation result = 88 (ASCII)
(5) BCC calculation formula = Modbus RTU
Calculation result = 85h 0Fh (binary)
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