We don't have a way of qualifying the data if the size of the last transaction is smaller than the bus width.
Since the requirement and the packet sizes that will be sent are known based on the end design it is up to you to implement a logic by which both sides sync up i.e. pad the data, send the byte count as part of the packet etc.
OK, I see. So we' have to insert some stuff bytes at the end of the packet if necessary and analyze the packet length in the protocol header.
Thank you for your quick reply!