M40 Profibus : read/write acyclic process data

Hi all,

We are using several types of M30 and M40 modules for several years but used always cyclic process data. We made our own anybus driver because our older instruments uses Pascal and everything works fine.
Now we need to read/write 4bytes (representing a status), defined in a separated ADI that is also mapped as process data. We want to access those 4 bytes acyclic to avoid always to send the whole process data over SPI.
Like I understand, reading the manual, it is possible to access process data acyclic with a message?
But it isn’t clear for me how to do this: with which object, instance, command? I hope it is for all kind of modules the same? At the moment we are testing it with a Profibus M40 module.
Can someone show me the right direction?

Thx, Peter

Hi Peter,

The data already mapped to process data? The process data is already exchanged every cycle over spi. Any additional data such as messages for Acyclic data, is added on to the process data.

The message to read and write the data acyclicly is setup on the Network side via the slot and index of the adi as seen in the network guide.

Thnx for some explanation. So it’s the network side who decides if the data is read or write acyclic, not the application?

Maybe I need to explain my problem better:
My application has 200 bytes (results) that only changes 1 times every 10 seconds. Beside those 200 bytes, my application has now also 4 bytes (status) that changes every 100 millisecond. Both data (200 bytes results & 4 bytes status) should be available on the network.
I’m working with SPI communication so sending 200 bytes takes much more µController power than sending only 4 bytes. My goal is that the application only need to exchange those 4 bytes every 100 milliseconds with the anybus module while only 1 time every 10 seconds I need to transmit 200+4 bytes over SPI to the anybus module. Is this possible and how?

Thnx for your help :wink:

From my understanding of our driver there is not an option to have two update times. I would recommend opening a support case on support.hms-networks.com Your local support team may have more input and be able to discuss this with the Anybus embedded team.

Ok, thanks for helping.
Br, Peter;)