Polling modbus

[FRRO]

Hi,

I'm using Lookout with a zetron 1700 controller who is communicating with 20 Zetron RTU station.

I want to poll every time there is a change on a RTU Station.

How should program lookout?.

Tx

[Ollie]

My understanding of the way the Zetron 1700 controller works is: If there is a change in one of the twenty RTU stations then that station reports the value change (REPORT BY EXCEPTION). Lookout using the Modbus protocol POLLS the Zetron 1700 controller's registers for value updates. Lookout does not talk directly to the RTU's in the field. The Zetron 1700 acts as a data concentrator so to speak.

In my opinion, you will not see any drastic performance gains trying to get Lookout to report only when there is a change and I don't think it is possible to do.

Oliver Scheurer
Aegis Solutions, Inc.
2660-T Yonkers Rd.
Raleigh, NC 27604
919-861-0103 x 231 (voice)
919-861-0104 (fax)
oscheurer@aegis-solutions.com

[Khalid]

Actually it is possible for Lookout to respond to only when there's a change. This is implemented using the Report-by-Exception ("unsolicited messages") functionality of Modbus protocol. To set this up in Lookout, you check this option under Advanced settings of the Modbus object.

With this setting, the device would "call back" the Lookout Modbus object asking "hey, my data has changed, please poll me." Then the Lookout Modbus object would schedule a poll to the device and get all data.

Hope this helps,

Khalid