DP in control system


Thread Starter


what is DP in control system? (abreviation and clarification)
Also what is profibus-DP?
Please help me.
Best regards
DP stands for Decentralized Periphery.

It is basically refering to a high speed RS485 network of slaves (remote I/O) that Daisy chain back to a central Master PLC.

Daniel Chartier

You will find a lot of technical info on Profibus on the PTO (Profibus Trade Oragisation) at "www.profibus.com":http://www.profibus.com .

Basically, Profibus is a simple(to configure protocol that appears in 3 formats:
- DP (= distributed periphery; the most popular type)for binary and analog values exchange (remote I/O)at high speeds (up to 12 MB) over RS485 2-wire cable;
- FMS (= field message specification; less popular)for master-to-master (peer-to-peer) communications, also on 2-wire RS485 cable;
- PA (= process automation; requires a DP setup to function)to access data from instrumentation transmitters and EX-zones; works in the same areas as HART or Fieldbus Foundation.

Hope this helps,
Daniel Chartier

Ranjan Acharya

I would recommend a search engine such as Google. You will find a wealth of information on PROFIBUS-DP (decentralised periphery). You could also try "http://www.profibus.com/":http://www.profibus.com/ . For an independent look at PROFIBUS or most other buses, start at "http://ourworld-top.cs.com/rahulsebos/index.htm":http://ourworld-top.cs.com/rahulsebos/index.htm .

The Internet has everything you need.

In my experience, most PROFIBUS field devices work really well with S7 masters. They start to mess you around if you are using a non-S7 master.
It was after all developed by Siemens.::

Ranjan Acharya, P.Eng
Team Leader - Systems Group
Grantek Control Systems
>In my experience, most PROFIBUS field devices work really well with S7
>masters. They start to mess you around if you are using a non-S7
>It was after all developed by Siemens.

Neither of these statements are true. We've sold several thousand Profibus slaves now over 4 years, and have had 5 problems requiring site attendance in all that time. 4 of these 5 were with Siemens equipment, but all but one due to configuration mistakes and cleared in a matter of minutes once a line analyser had been applied. In my experience, the masters from Hilscher, SST,
Softing, and so on work very well, and indeed I believe the SST PLC/5 master was the first certified master implementation. We've seen odd problems with cutting edge parts of Profibus - DPV1 for example - but DP is rock solid and very easy to apply.

As to Siemens developing Profibus, this is simply false. It was developed by a German consortium and later adopted by Siemens (amongst others). Siemens do provide the chipset most often used in slaves and masters, but this causes no practical difficulties - Profibus DP is genuinely open to all, and the wide support by many vendors is clear evidence of this. My company competes with Siemens to provide PID loops on Profibus, and it's a very easy way onto their backplane.


Tim Linnell (Eurotherm)

Ranjan Acharya

A follow up ...

My original statements: "In my experience, most PROFIBUS field devices work really well with S7 masters. They start to mess you around if you are using a non-S7 master. It was after all developed by Siemens."

"Neither of these statements are true" according to another post.

I was wrong, PROFIBUS was not developed by Siemens. I am not an expert on the history of who developed what bus and when. Sorry, I should have kept my cake hole shut. I was just being cheeky and making a subtle complaint regarding the whole field bus mess where each manufacturer (or arms length consortium) got their bus on the standard but OPC-DX aside they are not interoperable. I get tired of the sales brochures pushing each bus as THE
standard bus.

The first statement is however TRUE, I was specifically making reference to a very recent experience with all-Siemens PROFIBUS devices, perhaps I should have elaborated further.

Here is the elaboration:

Just try and use some Siemens-made ET200M I/O cards (specifically encoder inputs) with a non-S7 master such as the Siemens-made 505 line (was TI, now Siemens) of PLCs. They just do not work together. This is not a problem with the PROFIBUS standard, but both ends are Siemens-made PROFIBUS-DP and they do not work together, so it must be a PROFIBUS implementation problem. QED. Let me know if the encoder card will work ... it will save my customer a bundle of cash.

I did not make this up. It is from Siemens via our local (and extremely knowledgeable) Siemens representative. We have and ET200M system being
attached to a Siemens SIMATIC 555-1106 CPU via the front port of the PLC (not FIM in this case). We have a 100 kHz encoder signal that we have to deal with. We have to use an ET200S encoder system instead of the ET200M. I tried to use all ET200M but we were told NO WAY. Using all ET200S is not a suitable alternative because it is clunky and has a really low I/O density for discrete signals.

At the end of the day, hairs could be split blaming a particular area of the system, but it appears that PROFIBUS-DP out in the wild is not as
interoperable as it makes out to be. If you have two components and they don't work together, then there are interoperability problems.

For our TI505 customers, we always ask the PROFIBUS-DP device vendor if their device works with the TI505 (front port and / or FIM).

There are also architectural issues such as TI I/O numbering that must be dealt with (boundaries of eight, wasting bases instead of slots with FIMs
and VFDs and so on). This is because of the way the TI PLCs are designed and not the fault of PROFIBUS. A pain in the neck nevertheless, which does not help PROFIBUS. There is always Control Technologies' DeviceNet card for the TI505. I think that their soon-to-be-released new version of their Ethernet adapter will support EtherNet/IP. They only need ControlNet and we
are all set.

When I read your question - what is DP - my first thought was of process control = where DP stands for Differential Pressure.

I'm not sure if that's what you meant, because Profibus DP is an entirely different animal - one which the previous commentors have defined.
The term decentralised is actually a translation from the German and they call DP "Dezentrale Peripherie". I think that "Decentralised Peripherals" is just a translation and that more information will be found on the subject by looking for "Distributed I/O - Master/Slave Networks". The PROFIBUS DP system was designed to make a faster, more efficient and cheaper way to connect multiple masters and slaves.

Hope that this helps a bit.