PLC-side Modems

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

How to enable a controller to communicate via landline or GSM/GPRS modem

Preparing the modem as described below initializes it so that it is compatible with Unitronics PLCs.

1. Connect the modem to a PC, using a cable comprising the full RS232 pinout, either supplied in the modem kit or supplied by the modem manufacturer.
   
   Note that using a cable that does not comprise the full RS232 pinout will cause the process to fail.
    

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.
         

        Enhanced Vision Division: Recommended Baud Rate is 57600.

      • 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. Initialize the PLC port using a COM Init FB, located on the COM menu.

   

    

   Parameter Name	Purpose
   Com Port	Select the physically linked Com Port.
   Baud Rate	Set the baud rate in COM Init to 57600: When working with Enhanced Vision PLCs. When working with V120/230/260/280/290 (monochrome) together with modems Enfora orTC65. In all other cases, 9600 is suitable.
   RS232 Time Out	This is the time that the PLC will wait for the modem to reply.
   Flow Control	This is generally left OFF.
   Ignore break	When working with Enhanced Vision PLCs, select Ignore Break
   Modem Settings
   Modem Type	Click to select the desired modem.
   Initialization strings	Click to edit if required.
   Dial Type	Set to Tone by default.
   Time Out Reply	When working with Enhanced Vision PLCs, set a minimum of 6 seconds.
   PIN Code	If your provider requires a PIN code, enter a constant number or link to MI. Note that the MI value must be in hexadecimal. For example, the PIN code 1111 requires a vector of 2 MIs containing the value 3131 3131. The vector should be terminated with 'null'.
   Clear SIM	Select this to clear the SIM card when COM Init is activated.

    

   Notes ♦	COM Init is generally performed once in a program.  It is usually a power-up task, however a one-shot transitional contact may also be used.
   ♦	The initialization commands must match the commands used to initialize the PLC modem.
   ♦	You can cause the modem to delay between initialization commands by typing WAIT, followed by the number of seconds; up to nine seconds is supported.
   ♦	Communications cannot flow through the port during initialization.
   ♦	The PLC cannot answer incoming calls when it is in bootstrap mode.
   ♦	The Answer Settings parameter, by default, enables the modem to answer incoming calls. This enables you to download an OS to the PLC via modem. However, you can enable the PLC to answer instead. To do this, locate the initialization string ATS0=1 and enter 0( ATS0=0). When ATS0=0, an OS cannot be downloaded.

4. 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 COM Port initialization SBs 80-85.
   ♦	COM Init  may take approximately a minute to complete.

    

   

5. Download the application to the PLC.

6. Connect the modem to the PLC.

After the modem is enabled and successfully initialized by the PLC (SBs 80, 82, 84 turn ON), the controller can either be accessed via modem or can dial a remote modem to establish a data link.

How to enable a PLC to dial a remote modem (Ladder)

Landline modems

GSM modems

How to terminate the link--Hang-up