In the fragmentation protocol we used there was one overhead byte for 7 data bytes. So 256 bytes in a fragmented frame would be 36 frames of 7 data plus one overhead byte, plus one frame of 4 data bytes and one overhead byte. With today's multi object CAN controllers you can automate this process easily.

http://kom.aau.dk/~jdn/edu/doc/fieldbus/devicenet/v1Ch4.PDF
Read the section on the fragmentation of I/O messages.

hi im trying to acces the url that you have posted but it is not working. any chance you still have the docs?

 

hi im trying to acces the url that you have posted but it is not working. any chance you still have the docs?

I don't have access to the original documents, but you can:

1. Acquire your own copy of the DeviceNet Specification
2. Keep searching for DeviceNet Fragmentation Protocol

I may be able to answer a specific question if you have one.