Quartus® Prime Pro Edition User Guide: Platform Designer

ID 683609
Date 7/08/2024
Public
Document Table of Contents

6.1.4.3. Avalon® Memory Mapped Unaligned Burst Expansion Bridge Example

The following example shows an unaligned read burst command from a host that the Avalon® Memory Mapped Unaligned Burst Expansion Bridge converts to an aligned request for a connected agent. The figure also shows the suppression of words due to the aligned read burst command. In this example, a 32-bit host requests an 8-beat burst of 32-bit words from a 64-bit agent with a start address that is not 64-bit aligned.

Figure 251. Unaligned Burst Expansion Bridge


Because the target agent has a 64-bit data width, address 1 is unaligned in the agent's address space. As a result, several smaller burst transactions are needed to request the data associated with the host's read burst command.

With an Avalon® memory mapped Unaligned Burst Expansion Bridge in place, the bridge issues a new read burst command to the target agent beginning at address 0 with burst length 10, which requests data up to the word stored at address 9.

When the bridge receives the word corresponding to address 0, it suppresses it from the host, and then delivers the words corresponding to addresses 1 through 8 to the host. When the bridge receives the word corresponding to address 9, it suppresses that word from the host.