If your PC is unable to communicate with a remote PLC via modem, refer to the table below.
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.
♦
Internal modems must be used in conjunction with the driver provided by
the modem's manufacturer.
Problem |
Possible Cause |
Recommended Action |
Modem fails to initialize |
PC-to-modem cable |
Make sure that the cable is securely connected, and that it is the original cable that was supplied with your modem. |
|
Incorrect initialization commands |
To learn how to edit initialization commands, refer to Configuring my PC's modem. |
|
Incompatible communication settings |
Most modems automatically match the parameters of incoming data: baud rate, data bits, parity & stop bits. The U90's modem communication settings are: 9600, 8 data bits, no parity, 1 stop bit. You may need to manually change your modem's communication settings to match these. |
|
Incorrect Com port |
Assign the correct modem Com port. Refer to Configuring my PC's modem. |
|
Com port not enabled |
Check that your PC communication port is enabled. This means checking your PC's BIOS/CMOS setup. |
|
Com port occupied |
Close the application that is accessing the port. |
Modem initializes, but no connection is established |
Remote PLC's modem failed to initialize |
Refer to PLC-to-Modem connections |
|
Remote PLC is not connected to modem |
Check that the remote PLC is connected to the modem. |
|
PLC-to-modem cable |
Make sure that the cable is securely connected, and that it is the original cable that was supplied with your modem. |
|
Modem is not connected to telephone line |
Check that the modem of both the local PC and the remote PLC is correctly connected to a functioning telephone line. |
|
Incorrect phone number |
Check the PC modem Phone Book. Refer to Configuring my PC's modem. |
|
No power supply to modem |
Check the power supply to both the PC's and the M90's modem. |
Modems connect, but the PLC's modem does not answer. |
PLC's modem did not initialize |
Refer to PLC modem communication problems. |
|
PLC-to-modem cable |
Check the pin-out of the PLC-to-modem adapter cables. Note that if you use cables comprising this pin-out, you must set the PLC's RS232 parameter Flow Control to N (none). |