Publication 1764-UM001B-EN-P - April 2002
Communication Connections 4-5
Using a Modem
You can use modems to connect a personal computer to one
MicroLogix 1500 controller (using DF1 Full-Duplex protocol), or to
multiple controllers (using DF1 Half-Duplex protocol), or Modbus
Slave RTU protocol, as shown in the following illustration. Do not use
DH-485 protocol through modems under any circumstance. (See
Using Modems with MicroLogix 1500 Programmable Controllers on
page E-3 for information on types of modems you can use with the
MicroLogix controllers.)
Isolated Modem Connection
We recommend using an AIC+, catalog number 1761-NET-AIC, as
your optical isolator for Channel 0. See page 4-16 for specific AIC+
cabling information. Using an AIC+ to isolate the modem is illustrated
below:
Modem Cable
(straight-through)
Personal
Computer
Modem
Modem
MicroLogix1500
Controller with
1764-LRP
Processor
Protocol
DF1 Full-Duplex protocol (to 1 controller)
DF1 Half-Duplex Slave protocol (to multiple controllers when a
DF1 Half-Duplex Master is present)
1761-CBL-AM00
or 1761-CBL-HM02
User supplied modem cable
Modem
24V dc
MicroLogix 1500 provides power to the AIC+ or
an external power supply may be used.
MicroLogix 1500 with 1764-LSP
or 1764-LRP processor
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