# DNP 3.0 vs. MODBUS, Generic Description

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I need to know the advantages of using DNP 3.0 for a link to a SCADA system and How serve DNP 3.0 using OPC server --- Yo necesito saber que ventajas se obtiene al usar DNP 3.0 para comunicarme entre un PLC y un SCADA Christhian Quijada [email protected]

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#### Philip Wong

Modbus Advantages: Well known and widely used in all industries. Very simple to implement. The protocol specification is widely available DNP 3.0 Advantages: Used mostly in the Power and Water industries where reliability and time stamping of events is important. Sequence of Event (SOE) reporting, accurate to milliseconds. Open standard, Protocol specification is available to members of the DNP User Group. The quiescent unsolicited mode of operation is very efficient, can transfer large amount of data using very little bandwidth. Time synchronization of slave devices. Works over serial link, TCP/IP or UDP/IP. [email protected] http://www.ioserver.com/

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Philip gives a good overview. But he forgot one "key difference". I often get people asking me for Modbus-to-DNP converters - Why? Because one can buy a Modbus PLC or I/O block starting at us$99. I'm not sure what DNP starts at, but I'd doubt it's under us$500 (us$1000 even? Anyone with a low-cost DNP RTU, now's the time to speak). I can appreciate the LARGE difference between a$3000 DNP-aware RTU with agency approvals and optimized for solar/radio applications as compared to a PLC-Direct $99 micro-PLC you buy with a credit card on-line. I'm not saying they are the same. But users should go into these things with their eyes wide-open. An industry specific protocol like DNP (or IEC870 or SECS/GEM or ??) can be highly optimized and effective at doing what you need done. Just be aware that it limits your purchase options and inflates your equipment purchase costs. Bottom line is the DNP 3.0 aware stuff probably will save you lots of time in installation, operation, and maintenance of your power/water system. That's it job. Just make sure you won't spend the next 5 years of your life looking for Modbus-to-DNP converters because you don't like the equipment selection or price tag of the DNP 3.0 stuff. Best Regards - Lynn Linse D #### Darold Woodward There are many advantages to DNP 3.0 from a communications protocol and operation standpoint. The primary one is that DNP supports both polled and unsolicited report by exception that dramatically increase the efficiency of the communications between master and slave. There are at least two DNP 3.0 i/o servers for PC-based HMI applications. Try the DNP website at www.dnp.org for more information. Darold Woodward PE SEL Inc. [email protected] D #### David Bowerman Lynn. I shall speak now..... Our company produces a lower cost DNP 3.0 RTU. We have several units which all support DNP3.0 and can be programmed with an IEC 1131 compliant software package.. they start at$1650 Aust Dollars so that for any one in Europe or the US they are a steel...

If your interested look at hunterwatertech.com.au you may be surprised..

David B