A.2 Protocol Description Appendix A: Communication
284 493-0736-11 (6-2)
information. The basic format always starts with the STX (start of text) as shown,
followed by bytes for:
• The destination address
• A stamp (indicating if the message is a retransmission)
• The message type
• The message
• End of text (ETX) character
• A checksum block check count (BCC)
Explanation of Terms
Terms used in the explanation of the message types and the ASCII characters used
are as follows.
STX – Start of text. This is an ASCII character with the value 02H (the symbol H
is used to indicate hexadecimal value) and indicates the start of a message.
Destination Adress – This address indicates which controller the message is
intended for. The address consists of two characters that have values between 00
and FF. Since the master identity is always 00, the slave station identities begin
with 01.
Example: To address station 24:
Decimal 24 equivalent is 18H. The ASCII code for 18 is:
1=31H
8=38H
0
STX
12
Destination
3
Stamp
4
Message
type
5 6 7 8
Start address
910
Number of
data bytes
11 N-2
Data
ASCII/binary
N-1
ETX
N
BCC
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