Automation Direct D2-DCM, Руководство пользователя

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D–2
Using the D2–DCM with Modems
Data Communications Module, 2nd Edition, 2/03
Introduction
There are some applications that require a remote connection to the PLC. These remote
connections require you to use a modem to communicate between the Personal Computer and
the PLC system. Although this manual tends to focus on using the D2–DCM in networking
applications, there are a tremendous number of people who simply use the D2–DCM as an extra
communications port. The D2–DCM provides additional flexibility in configuration and baud rates
compared to the built-in port on the CPU, so it’s a logical choice for use with a modem.
It is not hard to establish remote communications with a PLC system via a modem. This
appendix provides some guidelines to help you setup the communications link.
There are typically two types of communication paths for modem applications.
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Telephone modems
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Radio modems
Both serve the same basic function, which is to enable data communications over a long
distance. However, your choice really depends on your particular application. Radio modems
are typically more expensive and can be more difficult to use in some situations. But if you
don’t have phone lines or dedicated cabling in the area, your choice may be restricted to radio
modems anyway.
For the DL205 family of products, any system that is designed to handle modem
communications usually contains components from the following list.
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DL240 PLC System with D2–DCM
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PLC System with DL250–1/260 CPU bottom port
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Personal Computer
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2 modems (one on each end)
Telephone
Modems
Radio
Modems
System Components