RapidIO Intel FPGA IP User Guide

ID 683884
Date 9/15/2021
Public
Document Table of Contents

4.5.4.2. Preserving Transaction Order

Your RapidIO IP core Doorbell module has a Tx staging FIFO in any of the following situations:
  • You select Prevent doorbell messages from passing write transactions in the RapidIO parameter editor.
  • Your RapidIO IP core targets Intel® Arria® 10 and Intel® Cyclone® 10 GX devices.

If the module has a Tx staging FIFO, each DOORBELL message from the Avalon® -MM interface is kept in the Tx staging FIFO until all I/O write transactions that started on the write Avalon® -MM slave interface before this DOORBELL message arrived on the Doorbell module Avalon® -MM interface have been transmitted to the Transport layer. An I/O write transaction is considered to have started before a DOORBELL transaction if the io_s_wr_write and io_s_wr_chipselect signals are asserted while the io_s_wr_waitrequest signal is not asserted, on a cycle preceding the cycle on which the drbell_s_write and drbell_s_chipselect signals are asserted for writing to the Tx Doorbell register while the drbell_s_waitrequest signal is not asserted.

If you do not select Prevent doorbell messages from passing write transactions in the RapidIO parameter editor, the Doorbell Tx staging FIFO is not configured in the RapidIO IP core.