IDEC MICROSmart FC6A-C16K1CE, Руководство по связи, Страница: 96 / 252

5: U
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OMMUNICATION
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NSTRUCTIONS
5-20 FC6A S
ERIES
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OMMUNICATION
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ANUAL
FC9Y-B1730
Conversion Type
The BCC calculation result can be converted or not according to the assigned conversion type as described below:
Example: BCC calculation result is 0041h.
(1) Binary to ASCII conversion
(2) No conversion
BCC Digits (Bytes)
The quantity of digits (bytes) of the BCC code can be selected from 1 or 2.
Example:
Comparing BCC Codes
The FC6A Series MicroSmart compares the BCC calculation result with the BCC code in the received incoming data to check for any error in the
incoming communication due to external noises or other causes. If a disparity is found in the comparison, an error code is stored in the data register
designated as receive status in the RXD instruction. For user communication error code, see "User Communication Error" on page 5-43.
Example 1: BCC is calculated for the first byte through the sixth byte using the XOR format, converted in binary to ASCII, and
compared with the BCC code appended to the seventh and eighth bytes of the incoming data.
Example 2: BCC is calculated for the first byte through the sixth byte using the ADD format, converted in binary to ASCII, and
compared with the BCC code appended to the seventh and eighth bytes of the incoming data.
Note: On WindLDR, Modbus ASCII defaults to binary
to ASCII conversion.
Note: On WindLDR, Modbus RTU defaults to no
conversion.
Note: On WindLDR, Modbus ASCII and Modbus RTU
default is set to 2 digits.
0041h
Binary to ASCII conversion
“4”
(34h)
“1”
(31h)
2 digits
D0010:
0041h
No conversion
NUL
(00h)
“A”
(41h)
2 digits
D0010:
(1) BCC digits = 2
“4”
(34h)
“1”
(31h)
“4”
(34h)
“1”
(31h)
(2) BCC digits = 1
“4”
(34h)
“1”
(31h)
“1”
(31h)
Lower digit
“1”
(31h)
“2”
(32h)
BCC calculation range
“3”
(33h)
“4”
(34h)
Incoming Data
“5”
(35h)
“6”
(36h)
“0”
(30h)
“7”
(37h)
BCC
31h ⊕ 32h ⊕ 33h ⊕ 34h ⊕ 35h ⊕ 36h = 07h
“0”
(30h)
“7”
(37h)
BCC Calculation Result
Binary to ASCII Conversion
Comparison result is true to indicate that data
is received correctly.
“1”
(31h)
“2”
(32h)
BCC calculation range
“3”
(33h)
“4”
(34h)
Incoming Data
“5”
(35h)
“6”
(36h)
“0”
(30h)
“7”
(37h)
BCC
31h + 32h + 33h + 34h + 35h + 36h = 135h
“3”
(33h)
“5”
(35h)
BCC Calculation Result
Binary to ASCII Conversion
Comparison result is false.
Error code 9 is stored in the receive status data
register.