Batboard

Hi there,

We are currently working on a SCADA project which requires radio communication that is compatible with the existing Motorola ASTRO Hybrid Smartzone communication system. Our agent has proposed XTL5000 for this purpose.

There will be SCADA (Data Acquisition) servers in the control room and RTUs in several remote sites. The servers will be connected to the XTL5000 thru RS232, and similarly the RTUs will also be connected to its XTL5000 thru RS232. The SCADA servers will need to communicate to the RTUs using say MODBUS RTU protocol, thru the radio.

I am interested to know how does the SCADA Server initiate the communication link? How do the SCADA Server tell the radio to make the connection to a particular RTU's XTL5000?

Does the end to end link act like a leased line or PSTN network where AT commands are used to establish a link? Or are digital contacts required? Or is it all performed through DTR/DSR/DCD control?

We were also informed that a MOSCAD CPU is necessary in between the SCADA Server and the XTL5000? Any idea?

Thanks for your help.

The Moscad polls radios, evey Moscad unit or scada has an adress and whilst each radio recieves everything the RTU's ignore any messages not for them.
So if the Scada has a message for a particular RTU it sends out the address of the RTU to wake it up.

You actually will need a Moscad Gateway between the Scada and the radio

thanks Bruce1807,

That means, the system architecture should look something like this:


Between the MOSCAD and the Radio, they will be talking MDLC (Motorola Data Link Communication) protocol. But what about between SCADA and MOSCAD, and between RTU and MOSCAD? What protocol does the MOSCAD support?

My concern is, because, between SCADA and the RTUs, a proprietary protocol is used, so how can we communicate this over the radio network?

thanks again.

you will only need a gateway at the computer end as this is needed for the data polling and collection and has an ethenet in connection. It manages all the RTU and keeps them in
As for protocol you can use ModBus or MDLC but there are lots of protcol converters out there and your Scada package should be able to do ModBus.
You use FSK, DPSK, DFM and all sorts of ways to do the signal.

Thanks again.

That was really helpful.

But i think I m gonna need another MOSCAD IP Gateway on the other end, coz the RTU on the other end is not a MOSCAD RTU. And at cetrtain time, the RTU will have to 'call back' to the SCADA.

When an RTU wants to talk it just checks that the radio is not busy and away it goes. The radio sends a CTS to the RTU, obviously if there is other traffic the CTS is held

oic. that means I dun really another unit on the other end.

you shouldnt as long as the protocols are the same