questions about Profibus communicaion

Hello to all,

Ì don`t understand nothing about profibus and i`m trying to setup a system where i have a s7 1200 1214 CPU as a slave using a CM1242-5.

in all project i just need to exchange some data ( about 8 bits from the I\O port and  some REAL values

my question is in the configuration :  do i need to create a Data Block with the data that i want to exchange and set as a path for the communication like in the MODBUS TCP \IP ?

what kind of configuration i need to do?

can someone help me?

Kind Regards,

Nuno

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Split from S7-1200 Profibus communicaion.

The easiest way is to install the vendor created GSD file into your project.  Then from the hardware configuration, you can add the device and a telegram to make it easy to communicate and exchange information.

Check with your profibus device's vendor for the GSD file and options on how to use the telegram(s) with it. 

U_0a3b2321-b41e-40f0-8316-d8ba6bc914e4

Hello to all,

Ì don`t understand nothing about profibus and i`m trying to setup a system where i have a s7 1200 1214 CPU as a slave using a CM1242-5.

in all project i just need to exchange some data ( about 8 bits from the I\O port and  some REAL values

my question is in the configuration :  do i need to create a Data Block with the data that i want to exchange and set as a path for the communication like in the MODBUS TCP \IP ?

what kind of configuration i need to do?

can someone help me?

Kind Regards,

Nuno

thank you  for the help huggy_d1,

what is the GSD file that you talking about?- sorry but i`m not used to work with this.

thank you one more time,

Best regards

Search for your part # and GSD on the vendor web site (or google/bing/etc).  If the vendor is Siemens, you should have little trouble getting it to work.  If not, you need to contact that vendor for the gsd file.  Sometimes they have to send it via email rather than have it posted for everyone on their web site, at least that is my experience. 

U_0a3b2321-b41e-40f0-8316-d8ba6bc914e4

thank you  for the help huggy_d1,

what is the GSD file that you talking about?- sorry but i`m not used to work with this.

thank you one more time,

Best regards

 Hello;

U_0a3b2321-b41e-40f0-8316-d8ba6bc914e4

thank you  for the help huggy_d1,

what is the GSD file that you talking about?- sorry but i`m not used to work with this.

thank you one more time,

Best regards

 You should really take a few minutes to understand the network you will be working with. You will lose a lot less time asking basic and fundamental questions, and your development time will be faster.

One of the best sources of documents on Profibus-DP comes from Profibus International, on their website Profibus.com, in the Download section:

http://www.profibus.com/nc/download/technical-descriptions-books/downloads/profibus-technology-and-application-system-description/display/

Hope this helps,

Daniel Chartier

Everytime you have to deal with Profibus / Profinet you have a controller (example : S7300/1200/1500/Simotion) that is capable to communicate and command a certain number of slaves ( HMI,Remote IO, Inverters, Sinamics, Robots, Weight measurer, ecc ecc ecc ecc ecc).

The problem is that the controller "doesn't know" what are the slave characteristics, how it communicate, the speeds it is capable to communicate and the billion of complex parameters that normally are better to leave as default that the slave can eventually handle.

To let the controller "know" how one slave is made the Minds of Profibus/Net invented the GSD  which is a simple txt-like file (often coupled with a BMP file for graphicrepresentation but it is not essential) that contains all the above mentioned infos.

You have to find (internet ? CD/DVD that is with your slave ? Already in the TIA Poratl GSD list ?) the EXACT gsd of your device and simply drag and drop into you project.

After that you have to define the exchange area, but this is another small but essential chapter.

This is the beginning of every Profibus/Net insertion of a new Slave , but as many guys said it is great to better understand some mechanicsms of the Profibus because they can really save time during installation.

Regards

thank you for the tips ChristophD !

i saw the GSD file and after i add the 1242-5 slave module and i drag and drop the file in to it. i didn`t saw any special change but i assume that that`s it.

now i define a data block where i place all the data that i want to read and wright ( about 15 bytes), but how i call it on the module?

i will not comissioning this as i just need to supply the system ready to communicate . some work must be done on the site but will be done by other company.

my question is to left this ready to communicate, besides the adress that i alredy define, i don`t know how i tell to the moule the place where he must reed and wright the data.

I`m sorry one more time if this questions are silly...

Best regards to all

Nuno

If you want to make a slave then all you have to do is configure I-slave transfer area in HW configuration of profibus slave module. You can R/W data from transfer area like R/W to input/output peripheral bytes/words of PLC.
The GSD file goes to the master (can be other simatic PLC or 3rd party PLC) HW caonfiguration, you don't need it in yours HW conf. But on the master side, there should be configured the exact the same sequence of transfer I/O data.

Look an example here: http://www.dynalogindia.com/wordpress/wp-content/uploads/2015/10/Moxa_Tech_Note-MGate5101_S7-1200.pdf

Haha, I am not ChristophD, he is another GREAT member of these forums and he is the most powerful user that handles Siemens with ease.

Don't worry for your "silly" doubt because when you understand it you have understood the Profibus basics and you will no longer have troubles.

Profibus is made by two parts  :1 assigning the GSD , 2 allocating the communication slots

Ok you are at step two.

First of all don't confuse or mixe the data blocks (DB i.e. DB50 DB60, ecc) with the periphery, this is another programming step.

Second you do not write no code that connects ur DB to your slave module. This will be done in the program of the PLC (FC, OB, ecc)

Now go to your problem:

Hard to reply with 101% of security because I don't know the size of your data. I make you two examples:

Slave is a Sinamics G120 Inverter in Profibus/Profinet. We know that he wants two words and he gives us back two other words.

First word we write (so it is a Word out) is the Setpoint

Second word we write (again another Word Out) is the flags settings

First word the G120 writes to us (so basically we READ it in the G120) is the status bit so it is a Word In for the PLC

And the same is for the second Word

So what is the configuration of words ?

PIW 100 and PIW 102 for READING the G120 status words

PQW 80 and PQW 89 for WRITING the G120 Speed and flags.

Note: I have intentionally put crazy numbers (100, 102, 80,89) because I want that you understand that basically you are not forced to assign a PIW/PQW location(s) consequent or in a special place, of course it is better because it is more clear, but it is not mandatory. PLC only wants that that locations are not used by another device , but this is reasonable.

From now when I want to write the Speed of inverter I do this :

PQW102:=DB321.DBW5;

Game over.

Second example:

My slave is a stupid card that reads out the temperature and gives it in Word format.

She has just one Word because we don't need other strange data to be exchanged (we just need the temperature).

So I import the GSD and in the data exchange area I define the PIW 907 (again a random location).

The slave does not care if the PLC is reading the data at 907 or 709 or 100 or 1. The Slave must only know that he will have to send ONE WORD. IF you are able to add more words in the slave then you must add the same number of words in the PLC, example:

5 words from slave ---> 5 PIW in the PLC

otherwise Profibus will give an error because one is writing 5 things and the other is expecting 9 I.e.

ohhhh... finnally i get it i think!

thank you all for the support!!!

With My best regards

Nuno