Altera RapidIO MegaCore Function - Manual (Page 191)

Appendix C: Porting a RapidIO Design from the Previous Version of the Software C–3
Upgrading a RapidIO Design to the Arria 10 Device Family
August 2014 Altera Corporation RapidIO MegaCore Function
User Guide
■ You must support a DOORBELL module Tx staging FIFO to support order
preservation between DOORBELL messages and I/O write request transactions.
Refer to
“Doorbell Slave” on page 3–7 . This change might affect resource
utilization but does not affect connections.