Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 209)

Publication AG-UM008C-EN-P - February 2005
Configuring MicroLogix 1000 Controllers 6-5
The following baud rate limitations affect autoswitching:
•
If the configured DH-485 baud rate is 19200, the configured DF1
baud rate must be 4800 or greater.
•
If the configured DH-485 baud rate is 9600, the configured DF1
baud rate must be 2400 or greater.
If your DF1 half-duplex slave baud rate is 1200 or less, and if your
process can tolerate a brief power cycle of the MicroLogix 1000
controller, you may set DH-485 as the primary protocol (S:0/10=1).
Upon power cycle, if your programming computer is attempting to
communicate using DH-485 protocol it will successfully go online.
Otherwise, if the modem is connected, upon power cycle the
MicroLogix 1000 controller will automatically switch from DH-485 to
DF1 protocol.
Using Modems that Support
DF1 Communication
Protocols The types of modems that you can use with MicroLogix controllers
include dial-up phone modems, leased-line modems, radio modems
and line drivers. For point-to-point full-duplex modem connections
that do not require any modem handshaking signals to operate, use
DF1 full-duplex protocol. For point-to-multipoint modem connections,
or point-to-point modem connections that require RTS/CTS
handshaking, use DF1 half-duplex slave protocol. In this case, one
(and only one) of the other devices must be configured for DF1
half-duplex master protocol.
IMPORTANT
Do not attempt to use DH-485 protocol through
modems under any circumstance.
IMPORTANT
Only Series D or later MicroLogix 1000 discrete
controllers and all MicroLogix 1000 analog
controllers support RTS/CTS modem handshaking,
and only when configured for DF1 half-duplex slave
protocol with the control line parameter set to
Half-Duplex Modem. No other modem handshaking
lines (i.e. Data Set Ready, Carrier Detect and Data
Terminal Ready) are supported by any MicroLogix
controllers.