HARDWARE
12
3.3 Using a Modem
These instructions are for a
U.S. Robotics
modem product # USR5686D or equivalent with
auto answer feature.
If using Modbus protocol, use ASCII mode. RTU mode has tighter timing requirements that
might prevent communications while using the modem. ASCII mode is enabled by
configuration switch S1-4 in the ON position. Enable the RS-232 handshaking lines by
setting the configuration switch S1-6 to the ON position. Connect the modem to TB11 as
detailed in Figure 8. Set the baud rate to 9600 bps by setting the configuration switch S1-7 to
the OFF position. Set the modem up for the settings listed below. The telephone cable plugs
into a standard analog phone line. This modem will not work with office digital phone
systems. The telephone line needs to be a dedicated analog phone line similar to most fax
machines. Plug in the AC power supply. The host software needs to have the same protocol
and serial parameters as the communications option.
Modem DIP Switch Settings
Switch
Position
Setting
1
Down
Data Terminal Ready override
2
Up
Verbal result codes
3
Down
Display result codes
4
Up
Echo offline commands
5
Up
Auto answer on
6
Up
Carrier detect normal
7
Down
Load factory defaults
8
Down
Smart mode
