Whats the difference between Consistent Profibus data in DP coupler?

Hi all,

The questions in the title really. I've been looking at a problem on a profi network. There is a DP/DP Coupler with 'consistent' data in the local hardware config. In the other PLCs hardware config the same data areas are set up but they are not 'consistent'.

My questions are... does this matter (I presume it does because it's not working)? And, if so, what's the difference between 'consistent' and 'non-consistent' data with regards to a DP coupler.

I'm getting the feeling that the answer is going to be really obvious and I should know this but... I don't. So be gentle with me...

http://cache.automation.siemens.com/dnl/Tk/Tk2MzQ4NQAA_28991143_FAQ/28991143_Consistent_Data_e.pdf

This document might help to explain data consistency.

If you transfer 16 words via your DP/DP coupler and they are marked as consistent then you should read/write all 16 words simultaneously via SFC14/SFC15. If you write to one of these words directly in the cyclic program then you run the risk of the whole consistent packet being invalid and therefore ignored.

Nick

Nick, many thanks for your excellent answer and link. I'm reading and digesting as we speak.... ;-))

You can think of consistent data as being a sentence. If you transfer and read it 'not consistent' (=fragmented) , there could be time periods that the content is mixed, both from the old and a new sentence, and tfehorere is misneaglnes.


Kalle

KalleOlsen said:

... tfehorere is misneaglnes.

Click to expand...

ha ha!

Thanks Kalle