Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 323)

Publication AG-UM008C-EN-P - February 2005
Using Dial-up Telephone Communication 10-3
Setting up the System Before you can begin sending messages over the telephone line, you
must:
•
configure the processor
•
configure the modems
Configure the Processor
Configure the processor’s serial channel for full-duplex DF1 protocol
and full-duplex modem handshaking (except MicroLogix) using
RSLogix software.
For example configurations, see the chapter in this book that pertains
to the processor you are configuring.
Configure the Modems for the PLC-5, SLC, and Logix Processors
Three RS-232 control signals are critical to the operation of dial-up
modems with PLC-5, SLC and Logix processors (when channel zero is
configured for full-duplex modem support): Data Set Ready (DSR),
Carrier Detect (CD), and Data Terminal Ready (DTR). DSR and CD are
signals that the modem produces and the attached processor or
module senses, while DTR is a signal the processor or module
produces to control its dial-up modem. DSR must be configured in the
modem to be on (or high) whenever a modem connection exists and
off (or low) otherwise. CD must be configured in the modem to be on
(or high) whenever a modem carrier from a remote modem is being
received and off (or low) otherwise. For DTR, the modem should be
configured to disconnect an existing connection when the processor
or module transitions DTR from on to off (or high to low).
This RS-232 control signal operation is configured into the dial-up
modem in at least one of three ways, depending on the model:
through switch settings, through pushbutton control panels, or by
sending standard AT ASCII commands to the modem’s RS-232 port.
The ASCII string to send to the modem that supports AT commands to
configure the RS-232 control signals to operate as described above is
as follows: AT &S1 &C1 &D2 Q1 E0 &W.
The ASCII string should be sent to the modem followed by carriage
return and line feed control characters. Note that the Q1 and E0
disable response codes and local character echo, and the &W saves
the configuration to the modem’s nonvolatile memory, if available.