Rockwell Automation 2755 Enhanced Decoder Series B - Manual (Page 189)

Chapter
15
Publication 2755-833
ASCII Host Commands
This chapter defines ASCII commands you can send from a host to
the decoder using the RS-232, RS-422, or DH485 communication
interfaces.
The RS-232, RS-422, and DH485 interfaces allow you to send single
or two character ASCII commands from the host to the decoder. All
commands and command responses are ASCII character strings.
The single character commands control scanning (Start/Stop Scan
characters), and the transmission (ACK/NAK characters) of data to
the host. They are not used to configure or monitor decoder
operations. The single character commands are configured on the
Host Communications screen described elsewhere in this manual.
The two character commands perform the same functions as the
settings on the configuration screens, and can be used to configure
and monitor decoder operations. The rest of this chapter defines the
two character ASCII commands.
!
ATTENTION: When controlling discrete outputs
locally using AUX port configuration, suspend host
communications to prevent outputs from
unintentionally changing state.
The DH485 interface supports the two character ASCII commands.
To use these commands, the decoder requires you to set the Host
Protocol parameter on the Host Communications screen to one of
the following:
•
DH485 ASCII-1 Protocol with Responses
•
DH485 ASCII-2 Protocol without Responses
Note: The DH485 ASCII-2 Protocol (without responses) reduces
data traffic on the link. Responses are unnecessary since the link
layer of the Allen-Bradley DH485 network insures that a command
is properly received.
The decoder supports the following DH485 communication
addresses:
DH485 LSAP Function
0 Diagnostic Commands (Perform Application Layer)
1 or 128 ASCII Commands (Perform Application Layer)
129 Perform Link Reset-immediate Block
Chapter Objectives
Using RS-232/RS-422
Using DH485