Profibus Dp v0-v1 and PPO type(cyclic-acyclic communication)

Hi everyone,

I have a project with S7-400H redundant system. All the communication with VFD's and SS's will be over using profibus protocol.

I am using IM153-2-Y link bundle to communicate field devices. So here comes my question, if ı use PPO type 5 and try to put all drivers to my profibus network, i get an error 'maximum area of 244 byte exceed'. I read the document of RPBA-01 again and again, ı choose the PPO type2 or PPO4 and it works for me.

Document of RPBA-01 says PPO1-2-5 are cyclic and PPO3-4 is acyclic. What is the difference between cyclic and acyclic communication. If i choose acyclic communication, should i have to use SFC14-15. Because when i use PPO5, i dont need the SFC14-15. Is acyclic communication need these SFC's?

My another question is; ACS800 profibus dp type is v0 ,What is the difference between v0 and v1?

 Hello desertfox;

rouk! has given you good basic information on DPV0 and DPV1; let's see if we can add answers to your other questions.

First point: a Y-Link acts (as far as the redundant DP masters on the S7-400H system can see) as a single Profibus slave, and has the limitations of a single slave: no more than 244 bytes and 244 bytes IN in the configuration. So the sum of the Profibus slaves data attached to the Y-Link must not exceed 244 bytes each way. Using PPO5 will require 28 bytes OUT/IN per drive, so you cannot place more than 8 drives attached to a single Y-Link (you can use more than one Y-Link per network). Using PPO2 or PPO4 reduces the amount of data exchanged per drive (since you do not reserve data area for the PKW section) so you can place more drives behind a Y-Link (but you exchange less data).

To see how the drive Profibus exchanges are generated (this is part of the ProfiDrive profile, see below), look at the following document describing the MM4 Profibus Option Board instructions.

https://support.industry.siemens.com/cs/ww/en/view/6586565

Notice the Profibus telegram structure is divided in 2 section, tht are accessed in different fashions:

- PKW (parameter values) can only be sent as a single telegram of 4 words, using SFC 15/14. This is nan acyclic communication pattern, requiring programmed functions in the PLC. They are used when you want to manipulate the drive parmeters online, over Profibus.

- PZD (process data) are controlled by the Profibus cycl;ic exchanges and are not linked to a communication function programmed by the user. They transfer control and status bits, and specified values of interest when monitoring the drive (current, speed...)

Notice how the manual explains which PPOx telegram uses both PKW and PZD, and compare them to the document you have been studying for the RPBA module

Hope this helps,

Daniel Chartier

Dear Daniel Chartier(dchartier)

Really really thank you for your answer, now many things are clear in my mind.

I read manual of RPBA-01 and really understand all the things.

So my last question; ı decided to use PPO4 and i will do parameter settings of driver from its panel. So all i need is reading and wrting PIW and PQW. I do not need SFC14-15. Am i right??

Again many thanks

Hello desertfox;

You will use SFC14 and SFC15 when you want to access various data from a slave over Profibus as a unit, like in a formal telegram. This is what you need to do when reading or writing parameter values (the PKW area discussed earlier).

But for a drive it is not necessary to do so when addressing the PZD area; you can read or write individually the different registers of the drive using peripheral addressing (PQW and PIW, as you mentioned).

Hope this hel;ps,

Daniel Chartier

Dear Daniel Chartier(dchartier)

I got it all, thanks for yor detailed explanation ;)