U90 Ladder Software Manual
78
Modems
About Modems
You can use the controller with either a PSTN modem or a cellular modem. When you use a cellular GSM
modem, you can also program the controller to both send and receive SMS messages from a GSM cellular
phone.
Before you can use modems in your application, you must use Modem Services to initialize both PC and PLC-
side modems.
Modem services
Modem Services is located on the Connections menu.
To use Modem Services, connect the modem to a PC, using the cable supplied by the modem manufacturer.
You can then initialize the modem.
Once you have connected initialized modems to your PC and PLC, you can use Modem Services to establish
communications with a remote PLC and perform tasks, just as you would if the PLC were directly connected to
your PC. For example, you can:
Dial a remote modem via Modem services.
Download, upload, and edit the controller program via the modem connection.
Run Online test mode.
Use OnLine test and Information Mode to troubleshoot problems in remote controllers and
applications.
Read and write data to/from controllers via Remote Access or Unitronics' communication .dll
utilities.
Receive and send SMS messages via SMS options.
Modem Tips
To avoid compatibility problems, use modems produced by the same manufacturer and of the same model. This
is due to lack of standardization between modem manufacturers, which may result in communication conflicts.
Note •
The PC-modem cable is not the same type of cable used to connect between the controller and
the modem. Ensure that the cable used to connect the PC to the modem provides connection
points for all of the modem's pins.
•
Jazz Controllers
Jazz controllers do not comprise an integral serial port. A Jazz controller
cannot be connected to a modem unless it has been installed with an
appropriate add-on port module.
Serial communications capabilities are determined by the type of Add-on
Module.
Default COM settings and pin-outs are given in the technical specifications
of the relevant Add-on Port.
The MJ20-PRG Programming Port may be used for RS232 communications
with devices that supply active (RS232 positive voltage) DTR and RTS
signals, such as most modems. Note that modems require an appropriate
adapter.
•
If calls are routed via a switchboard, note that the switchboard settings may interfere with
communications. Consult with your switchboard provider
•
If, within the modem initialization strings, the parameter S7 is too short to permit the PLC's
modem to answer, an error will result.
For example, if this parameter is set as S7=30, the PC modem will wait for 3 seconds to