Control.com - Nerds in Control

Dear all,
We have situation in which we would like to communicate (interrogate statuses and give commands) to one ABB RTU 400 speaking IEC870-5-101 with two master SCADA systems. These two Central systems will work as one is running in the normal circumstances and the other one shall have the latest database in order to be able to make necessary monitoring and control in case of emergencies when the 1st one fails. The 1st SCADA system is ABB SPIDER the 2nd one not defined yet.

I am not sure that ABB RTU 400 can be utilized in this project can any one advise.

Any Idea or similar implemented scheme?

Abd Al Hakam Zarzora
TRANSCO, Planning and Projects
abdalhakam@transco.co.ae

By its nature a Master/Slave system does not allow for two Masters. It's against the rules.

Rules are meant to be broken. I've gotten MODBUS systems to work with two Masters. If the Masters use hardware handshaking, RTS and CTS, then you can use a device to hold off one while the other communicates. The trick is to get the Master to leave the RTS on until it has received its response. Black Box had a device that could be made to work.

I hope this helps. If you need more information, let me know.

Lewis Bodden
LewisBodden@QuickWizEfactory.com

Another possibility is to use special hardware to share the single slave port. The Miille Applied Research "Port Multiplier" module http://www.miille.com/din366-10p.pdf can do this. Recognize that if both masters are trying to control the same point, there will be a conflict. The last one there wins.

Jerry Miille

Niobrara R&D has an SPE4 that would suit your needs just fine. The SPE4 has 5 ports, any of which can have a master or a string of slaves. The ports that the masters are connected to would simply single-thread the messages from the multiple masters.

Come check out our website at http://www.niobrara.com and use the "email tech support" link if you need more help.