Automation Direct D2-DCM, User Manual

Page: 72 / 83

D–6
Using the D2–DCM with Modems
Data Communications Module, 2nd Edition, 2/03
Choose the Proper Cables
The exact cables needed really depend on your particular application. In any case, you will
probably use one or more of the following connections.
D
Personal Computer to modem connection
D
Modem to D2–DCM connection
D
Modem to DL240 connection
Your choice of cable for connecting the modem to your personal computer depends on
whether you have a 9-pin port or a 25-pin port on your COM card. In either case, it’s usually
easier to buy a cable rather than make one. It is suggested that you check your modem
documentation to see what the manufacturer recommends. If your documentation does not
recommend a cable, you could try the following sources.
D
Radio Shack
D
Black Box Catalog
Some users prefer to build their own cable. Here are the pinouts that are usually required.
Again, check your modem documentation for the exact requirements.
NOTE: The 9-pin diagram can be confusing because it shows TXD – TXD and RXD – RXD
connections. This is actually correct because the 9-pin connector conforms to the IBM
standard for DTE and the 25-pin side conforms to the standard for DCE. This results in the
slight confusion over the terminology used to label the TXD and RXD pins.
2 TXD
3
7
4
RXD
GND
RTS
5 CTS
6
8
DSR
DCD
20 DTR
2 TXD
3
7
4
RXD
GND
RTS
5 CTS
6 DSR
8 DCD
20 DTR
RS232C
25 to 25 Pin Cable
2 RXD
3
5
1
6
TXD
GND
DCD
DSR
RS232C
4 DTR
7 RTS
8 CTS
25Ćpin Connector
9Ćpin
Connector
PC Modem
9 to 25 Pin Cable
PC Modem
25Ćpin Connector 25Ćpin Connector
2 TXD
3
7
8
6
RXD
GND
DCD
DSR
20 DTR
4 RTS
5 CTS
9 RI 22 RI
Connecting a Modem
to your Personal
Computer