[etherlab-users] EL6731 discontinuous PDO

[Thomas Paoloni]

Hi all,

I'm dealing with a domain containing a EL6731 (Profibus master) and 
obviously a Profibus subnet behind the 6731.
The PDO data referring the 6731 are in some way "blinking", the 6731's 
PDO area is filled wit zeros and periodically I can see the data 
exchangend on Profibus side.
The period of visibility is related to the time that the 6731 need to 
get a cyclic data from Profibus side.
I can see the Ethercat master changing his state from 1 to 2 and then to 
1 again (1=EC_WC_COMPLETE, 2=EC_WC_INCOMPLETE) and PDO of EL6731 are 
available only when it is EC_WC_COMPLETE.
I can assume that if 6731 doesn't have fresh data from Profibus side, 
doesn't exchange data either on Ethercat side and zeroes are returned 
over the old data.
Is there any method in order to avoid this "blanking" of the PDO ?
I would simply like to keep old data until a fresh one is available, do 
I need to buffer PDO myself or some function is available in order to 
obtain the same result in a more elegant way ?


Thanks,

Thomas.