IDEC MICROSmart FC6A-C16K1CE, Руководство по связи, Страница: 83 / 252

FC6A S
ERIES
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ICRO
S
MART
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LL
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IN
-O
NE
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YPE
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OMMUNICATION
M
ANUAL
FC9Y-B1730 5-7
5: U
SER
C
OMMUNICATION
I
NSTRUCTIONS
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
(2) Calculation start position = 2
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.
(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)
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)
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)
ASCII Data
“A”
(41h)
“B”
(42h)
“C”
(43h)
“D”
(44h)