Rockwell Automation 1770-KF2 Data Highway or Highway Plus Interface Module User Manual User Manual
Page 47
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Asynchronous Link Protocols
Chapter 4
4-4
Figure 4.1
Packet Format for Full-Duplex Protocol
CMD
STS
Command/Response Block
DST
SRC
CMD
STS
TNS
Data
(From Application Layer)
DLE
STX
Data
(From Network Layer)
DLE
ETX
From
Application
Layer
From
Network
Layer
11321A
BCC
Data Link
Layer Packet
Block Check
The block check character (BCC) is a means of checking the accuracy of
each message packet transmission. It is the 2’s complement of the 8-bit
sum (modulo-256 arithmetic sum) of all data bytes between the DLE STX
and the DLE ETX BCC. It does not include any other message packet
codes or response codes.
Example 1: If a message packet contained the data codes 08, 09, 06, 00,
02, 04 and 03, the message packet codes would be (in hex):
10
DLE
STX
02
08 09 06 00 02 04 03
10
03
E0
DLE
ETX
BCC
Data
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