I/O Device Constraints for Multi-dropping

If you are 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. 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 is capable of issuing caller IDs. If multi-dropping, use I/O Devices that can issue caller IDs.

1. Run the Device Communications Wizard.
2. Complete the wizard, selecting the relevant I/O Server, then the I/O Device, creating each new instance when necessary.
3. On the Scheduling page of the wizard, select the Connect I/O Device to PSTN check box.
4. Select an appropriate schedule for Citect SCADA to communicate with the remote I/O Device. (For a persistent connection - whenever Citect SCADA is running - select On Startup.) For example (all based on a Synchronize at time of 10:00:00):
• If you enter 12:00:00 in the Repeat every field, and start your project at 9 a.m., the I/O Server will communicate with the I/O Device at 10 a.m., then once every 12 hours after that; that is, 10 p.m., then again at 10 a.m. of the following day, and so on.
• If you enter 12:00:00 and start your project at 4 p.m., the I/O Server will communicate with the I/O Server at 10 p.m., then again at 10 a.m., of the following day, and so on. Citect SCADA will assume that communications were established at 10.a.m., so will continue as if they had been, communicating once every 12 hours after 10 a.m.
• If you enter 3 days and start your project at 9 a.m. on a Wednesday, the I/O Server will communicate with the I/O Device at 10 a.m., then once every 3 days after that; that is, 10 a.m. on the following Saturday, then at 10 a.m. on the following Tuesday, and so on.
• If you enter the 6^th of December in the Repeat every field and start your project during November, the I/O Server will communicate with the I/O Device at 10 a.m. on December 6, then again on December 6 of the following year, and so on.
5. Select On Startup for a persistent connection. To disconnect a persistent connection, call the IODeviceControl() function with type 8.
6. Type in the phone number necessary for Citect SCADA to dial the remote modem attached to the remote I/O Device. Include any pre-dial numbers necessary to obtain a connection to an outside PSTN line (dial tone) before dialing (for example, 0 (zero)) - if appropriate.
7. On the next wizard page, if the device is configured to dial-in to Citect SCADA, create a unique identifying caller name for the remote I/O Device so that it can be identified by Citect SCADA.
8. Follow the instructions on the next page of the wizard and click Finish.

See Also

Published June 2018