Response Frame; Bcc Calculation Example - Omron E5AN Communications Manual

● BCC Calculation Example
STX
Node number Sub-address
02H 0 (30H) 0 (30H) 0 (30H) 0 (30H) 0 (30H) 0 (30H)5 (35H) 0 (30H)3 (33H)
BCC = 30H+30H+30H+30H+30H+30H+35H+30H+33H+03H = 35H
The result of the calculation (35 hex) is written to the BCC byte.

■ Response Frame

Node number
STX
1 2
End
Name
code
00 Normal completion
0F FINS command error
10 Parity error
11 Framing error
12 Overrun error
13 BCC error
14 Format error
16 Sub-address error
18 Frame length error
• An end code is returned for each command frame received that was addressed to the local node.
• No response will be returned unless the frame contained all elements up to the ETX and BCC.
• "Error Detection Priority" indicates the priority when two or more errors occur simultaneously.
The BCC (Block Check Character) is determined by calculating the
exclusive OR of the bytes from the node number up to ETX. The 8-bit
result is written to the BCC byte at the end of the frame.
SID
The + symbols indicate XOR (exclusive OR) operations.
Sub-address End code
0 0
2 2
Description
The command ended normally without error.
The specified FINS command could not be executed.
The FINS response code should indicate why the command
could not be executed.
The sum total of bits whose received data is "1" does not
match the set value of the "communications parity" bit.
Stop bit is "0."
An attempt was made to transfer new data when the recep-
tion data buffer was already full.
The calculated BCC value is different from the received
BCC value.
• The command text contains characters other than 0 to 9,
and A to F. This error does not apply to Echoback Tests.
(Refer to the Echoback Test for details.)
• There was no SID and command text. There was no com-
mand text.
• "MRC/SRC" not included in command text.
• Illegal (unsupported) sub-address
• There was no sub-address, SID, and command text.
• Sub-address was less than two characters, and there was
no SID and command text
The received frame exceeds the specified (supported) num-
ber of bytes.
2.1 Data Format
Command text ETX
03H
Command text
ETX
detection
None
8
2
1
3
5
7
6
4
BCC
35H
BCC
1 1
Error
priority
2-3