CONFIGURING SERIAL PORTS
SNAP-LCM4 User’s Guide
17
COM0 Modem Configuration and Wiring
In RS-232 mode, COM0 also supports RTS and DTR/DCD flow control for use with modems, either with or
without a carrier detect. Check your modem documentation for additional wiring information, possible
jumper configuration, and initialization setup. You may also want to read Opto 22’s communication
application notes, available on the Opto 22 Web site or through our Bulletin Board Service. See page
for
details.
The following diagrams illustrate wiring for modems. Use the COM0 default jumper settings for modems
(shown in the diagram on page
Configuring Port 1
COM1 comes from the factory set up for communicating
with Opto 22 remote I/O. COM1 is a two-wire RS-485 port
only. It will not typically require configuration unless you are
using it with devices that are not Opto 22 remote I/O.
CFG1 jumpers control COM1. Default jumper settings are
shown in the diagram at right.
Pin connections are shown in the following table:
Pin
RS-485 2-wire
1
TX/RX +
2
TX/RX -
3
COM
4
IRQ +
5
IRQ -
Wiring to a Modem without Carrier
Wiring to a Modem with Carrier
COM1 Default Jumpers.
1
