Rockwell Automation 2755 Enhanced Decoder Series B - Manual (Page 194)

15–6 ASCII Host Commands
Publication 2755-833
Note: The start command sequence is optional. The <ESC>=!
sequence differentiates two character commands from single
character commands. If any of the characters below are used as
single character commands (ACK/NAK or Start/Stop Scan
Characters), then the escape sequence (ESC=!) must be used
with all two character commands that start with that
character.
A B C D H I M N O P R S T
If the single character commands do not use these uppercase
characters, you do not have to use the start command sequence.
For example, if N is used as the NAK command, then it would be
impossible to send the NR command without preceding it with
the ESC=! start command sequence. If n is used instead, then no
start command sequence would be necessary to send an NR
command. Therefore, we recommend using only lowercase
letters for single character commands.
Note: The start command sequence <ESC>=! is
not valid when sending ASCII commands using the DH485
interface.
2. Command Code. Two characters that specify the command.
3. Parameters. Data that further determines the command action.
Some commands do not have parameters.
4. Terminator. An ASCII control code (less than decimal 32) that
terminates the command. Typical control codes are: <CR>, <LF>,
<CRLF>, <ETX>.
Command Replies
The decoder sends a reply in response to each command sent from
the host. Command replies have the following structure:
1
Parameter 2
End of
Parameter
Code 3
=
4
Response
Code 5
End of
Message
Code
Note: The first two parts of the response may not be present
depending on the command.