Intel® Quartus® Prime Pro Edition User Guide: Platform Designer

ID 683609
Date 9/26/2022
Public

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7.1.4.1. Using the Avalon® Memory Mapped Unaligned Burst Expansion Bridge

When a host sends a read burst transaction to an agent, the Avalon® Memory Mapped Unaligned Burst Expansion Bridge initially determines whether the start address of the read burst transaction is aligned to the agent's memory address space. If the base address is aligned, the bridge does not change the base address. If the base address is not aligned, the bridge aligns the base address to the nearest aligned address that is less than the requested base address.

The Avalon® Memory Mapped Unaligned Burst Expansion Bridge then determines whether the final word requested by the host is the last word at the agent read burst address. If a single agent address contains multiple words, all those words must be requested for a single read burst transaction to occur.

  • If the final word requested by the host is the last word at the agent read burst address, the bridge does not modify the burst length of the read burst command to the agent.
  • If the final word requested by the host is not the last word at the agent read burst address, the bridge increases the burst length of the read burst command to the agent. The final word requested by the modified read burst command is then the last word at the agent read burst address.

The bridge stores information about each aligned read burst command that it sends to agents connected to a host interface. When a read response is received on the host interface, the bridge determines if the base address or burst length of the issued read burst command was altered.

If the bridge alters either the base address or the burst length of the issued read burst command, it receives response words that the host did not request. The bridge suppresses words that it receives from the aligned burst response that are not part of the original read burst command from the host.