Configuring multidrop remote I/O Devices

Multidropping remote I/O Devices from the same remote modem enables CitectSCADA to communicate with each I/O Device one after the other, using the same phone connection, rather than hanging up and re-dialing.

Although you can configure multidrop remote I/O Devices using the Express Communications Wizard, we recommend that you do it manually. The wizard would create a new port for each I/O Device. This would mean you couldn't have any more than 255 I/O Devices.

1. Run the Express Communications Wizard to configure the first device.
2. Configure every other I/O device manually.
3. Open the Citect Project Editor.
4. Select Communications | I/O Server and scroll to the I/O Server that will be communicating with the I/O Device.
5. Select Communications | I/O Devices.Complete the dialog box.
6. To increase the efficiency and capacity of your system you can allocate the same port name to I/O Devices with the same communication settings.

7. Note: If you are multi-dropping and you want to be able to dial in to the I/O Server, use your I/O Devices to issue the caller ID, not the modem. This is because using the modem to issue the ID will send the same ID no matter which I/O Device the call is relevant to. This makes it difficult to identify the I/O Device that triggered the call.

By using the I/O Device to issue the ID, the I/O Server will receive a unique caller ID for each I/O Device. However, not every I/O Device are capable of issuing caller IDs. If multi-dropping, use I/O Devices that can issue caller IDs.

You can connect multiple I/O Devices to the same modem. This means CitectSCADA can communicate with these I/O Devices one after the other using the same phone connection, rather than hanging up and re-dialing. This will reduce the number of necessary telephone calls and increase the speed and efficiency of communications.

1. Connect the modem to a PC with a telephony program installed (for example HyperTerminal or PhoneDialer). This is where you will configure the modem to answer calls from CitectSCADA and/or initiate calls.
2. If the modem is necessary to make calls to CitectSCADA, configure it to initiate the phone call to a pre-determined CitectSCADA I/O Server Dial-In type modem (following manufacturer instructions).
3. Depending on your hardware either the modem or an intelligent PLC can be responsible for initiating calls to CitectSCADA and identifying the caller. Whichever is responsible needs to have a caller ID set. The caller ID can be any combination of alpha-numeric characters and/or the character '_' (underscore).

4. Some modems have dip-switch settings, and some have initiation strings which can include auto-dial-up numbers that are stored within the modem's non-volatile memory. Consult the manual provided with the modem for exact details.

   You can use either the Express Communications Wizard or the I/O Devices form to set the caller ID for an I/O Device.

   If multi-dropping off a single modem, use your I/O Devices to issue the caller ID, not the modem. This is because using the modem to issue the ID will send the same ID no matter which I/O Device the call is relevant to, making it difficult to identify which I/O Device triggered the call.

   By using the I/O Device to issue the ID, the I/O Server will receive a unique caller ID for each I/O Device. However, not every I/O Device is capable of issuing caller IDs. If you are multi-dropping, use I/O Devices that can issue caller IDs.

4. Set the modem's Data bits, Parity, Stop bits, and Serial-Rate to match manufacturer specifications for communication with the I/O Devices.

5. Some modems do not allow you to manipulate their communications settings via methods such as extended AT commands or dip switches. If this is the case, the only way of setting the necessary values is to communicate with the modem using the values (for example, via HyperTerminal). Once this is done, the modem remembers the last values used to communicate with its serial port.

5. Connect the modem to the I/O Devices.

To configure a modem at the I/O Server you need to set it up in Windows and then set it up in CitectSCADA.

If every one of your I/O Devices are the same, you only have to do this once for each modem. However, if your I/O Devices talk using different communication specifications (data bitsGroup of binary digits (bits) used to represent a single character of data in asynchronous transmission., parityA communications error-checking procedure. The number of 1's must be the same (even or odd) for each group of bits transmitted without error., stop bitsThe number of bits that signals the end of a character in asynchronous transmission. The number is usually 1 or 2. Stop bits are required in asynchronous transmissions because the irregular time gaps between transmitted characters makes it impossible for the server or I/O device to determine when the next character should arrive., and serial-rate), your modem has to be able to talk using each of these details as well. To set this up, you have to create a modem in Windows and CitectSCADA for each specification. (See Example configurations for modems at the I/O Server)

1. Each modem connected to a CitectSCADA I/O Server PC needs to FIRST be configured within Windows using Start | Settings | Control Panel | Phone and Modem Options.
2. Select the Modems tab, and click Add to launch the Install New Modem wizard.
3. Check the box labeled Don't detect my modem; I will select it from a list, then click Next.
4. Select Standard Modem Types in the list of manufacturers.

5. Note: Do not select a brand name modem from the Manufacturers list, even if the name of the modem you're installing is included in the list. Do not click Have Disk.

5. Select the Standard xxxx bps modem rate from the list of models to exactly match the bit per second rate of the I/O Device that is going to be communicating via this modem. Check the device to determine the device communication rate. If you are still unsure, select the 9600 bps model. This can be changed later if necessary.
6. Do not click Have Disk. Click Next.
7. Select the COMx Port that the modem is connected to. Click Next.
8. Click Finish. Windows displays the modem in the list of modems on the Modems Properties form.
9. No option was given for the selection and setting of the Data bits, Parity, or Stop bits information. The Modems wizard automatically defaults to 8-none-1 for Standard Modem types. To change these settings to match the Data bits, Parity, Stop bits requirements of the remote I/O Device, select a modem in the list, then click the Properties button.
10. Click the Advanced tab and click Change Default Preferences.
11. Click the Advanced tab at the next dialog to gain access to the Data bits, Parity, Stop bits settings for the modem.
12. Change the Data bits, Parity, and Stop bits settings using the drop-down options, so that they exactly match those being used by the remote I/O Device and its remote modem. Don't change any advanced settings. (The default is Hardware flow control.)
13. Click OK. If a modem of the same rate is installed to the same port as an existing modem, Windows asks for confirmation that you want to install the same thing more than once. Click Yes to install a duplicate copy of the modem.
14. Preconfigure the modem(s) to be used at the remote dial-up I/O Device(s). These will be used to test modem configuration settings in the next step.
15. With CitectSCADA not running, confirm that the local and remote modems will properly communicate with each other by using a terminal communications program such HyperTerminal or PhoneDialer (both supplied with Windows).

Once the modem(s) are set up and tested with proven communications in Windows, they can then be set up in CitectSCADA.

Before completing this procedure, verify that you have set up your modem in Windows (as described above).

1. Open the Citect Project Editor.
2. Select Communications | I/O Server and scroll to the I/O Server the modem is attached to.
3. Select Communications | Modems. The Modem Properties dialog will appear.

1. The following fields are implemented with extended forms (press F2).

   Use this modem to call back I/O Devices

   Determines whether this modem will be used to initiate calls from the I/O Server to a dial-up remote I/O Device in response to a call received from the I/O Device. (Dial-Back)

4. Complete the dialog box.

5. Note: CitectSCADA allows you to set up a maximum of 256 modems on the I/O Server for communication with remote dial-up I/O Devices. Before it can successfully establish communication, any targeted remote I/O Devices need to also be properly configured within CitectSCADA on the I/O Server.