PLC-side Modems

The PLC can use a landline or GSM modem to send and receive calls. A programmer can also use a PC's modem to communicate with a remote PLC that is connected up to a modem.

Before integrating modems into your applications, check the section Modems-Tips & Cautions.

Enabling a Controller to Communicate via Modem

1. Connect the modem to a PC, using the cable supplied by the modem manufacturer.

2. Prepare the PLC modem.

   1. Connect the modem to a PC, using the cable supplied by the modem manufacturer.

   2. Open Connection>Modem Services, and select the modem type. If required, you can edit other parameters:

      • Com Port, baud rate, Time Out, and Time-Out Reply: use the drop down boxes

      • PIN code: click to enter the number.

   3. Click the Prepare PLC-side Modem button; that dialog box opens.

   4. If required, edit initialization commands by clicking in the field and entering text.

   5. When all parameters are set, click the Init Modem button; the PC establishes communication with the modem and initializes it.

   

    

3. Ensure that the PLC port is initialized via either SB 72, Modem Initialization, or SB 180 Initialize GSM Modem for SMS.

PSTN Modems

1. 1. Open the PLC Modem Configuration box by selecting Controller> PLC Modem Configuration.

   2. Check the 'Use PTSN Modem' box shown below. This causes the PLC to automatically turn on SB 72, Initialize Modem, at power-up. Note that:

   • If the Use Modem option is selected, at power-up the modem will be initialized with the customized strings and parameters that you selected during the Prepare PLC Modem procedure.

   • If the Use Modem option is not selected, the default Modem strings and settings contained in PLC Modem Configuration, shown below, will be used to initialize the modem.

1. 3. If your application requires, you can edit the initialization commands.

      • To edit initialization commands, click on the Edit Initialization Commands button shown below.
        The window containing the commands turns white; you can now add, delete or edit commands.

      Note ♦

      Applications previous to U90 Ladder 4.0. The Prepare Modem procedure was integrated into U90 Ladder starting with version 4.00. If you are working with an application created using an earlier version, you can restore the older, default modem commands by clicking the Retrieve Former Modem Strings button.

       

        
      
      You can also enter a wait command.

      

       

   4. The U90 Ladder default modem settings are: 9600, 8 data bits, no parity, 1 stop bit. If required, you can change the setting to match the Prepare PLC Modem strings by clicking Controller> PLC> Advanced button to open PLC Communication Settings, and then changing the parameters and selecting Force PLC Settings.

      

   5. Select whether to use pulse or tone dialing, as is required by your system, by clicking on the appropriate box. You can also leave both blank (default).

   6. You can also edit the modem's time-out settings.

      6. Display the Modem Time-out settings by clicking the Advanced button. Set the appropriate times as shown below.

      

   7. To enable the PLC to dial via modem, enter numbers in the
      Phone Book

      The Phone Book is where you define the list of numbers that the PLC can dial.

      You can enter up to six numbers. Each phone number is automatically linked to an index number. In your application, you store the index number of the phone number you want to dial into SI 71. Then, when SB 77, Dial, turns ON, the PLC dials that number.

      Each phone number can be up to 18 characters long. You can also add a description to identify the location or other details of the number to be dialed.

      Entering numbers in the Phone Book

      1. Click on an empty line in the Phone Book, then type in the number, exactly as you would dial from a standard phone, including area codes. To dial an outside line, enter the prefix number required and follow it with a comma as shown below.

         This comma causes the short pause, or delay, that is required by many systems.

         

         To edit the phone book, click in a number or description, then make your changes.

GSM Modems

1. 1. Under Controller>SMS Configuration, select Use GSM Modem. This turns on SB 180 Initialize GSM Modem for SMS. Note that there is no option Select Modem Type. This is because the controller automatically recognises the type of modem that is connected.

   2. Build a Ladder program containing the correct conditions and elements.

      Note ♦

      Communications cannot flow through the port during initialization. To avoid conflicts in your program, use the Modem Initialization SBs.

       

      

   3. Download the application to the PLC.

   4. Connect the modem to the PLC.
      
      After the modem is enabled and successfully initialized by the PLC (SBs 72 & 73 turn ON), the controller can either be accessed via modem or can dial a remote modem to establish a data link.

   5. To terminate the call, turn SB 76 Disconnect Modem ON.

Downloading, uploading, and comparing settings

Related Topics

Configuring my PC's modem

About modems

Direct Communications- PC to M90

PLC to Modem Connection and Cable Pin-out

Modem Troubleshooting

M90 modem communication problems

How the M90 works with a modem