External Memory Interface Handbook Volume 3: Reference Material

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ID 683841
Date 7/24/2019
Public
Document Table of Contents

6.12.1.1. Avalon-MM Bidirectional Port

The Avalon-MM bidirectional ports are standard Avalon-MM ports used to dispatch read and write operations.
Each configured Avalon-MM bidirectional port consists of the signals listed in the following table.
Table 78.  Avalon-MM Bidirectional Port Signals

Name

Bit Width

Input/Output Direction

Function

clk

1

In

Clock for the Avalon-MM interface

read

1

In

Indicates read transaction 8

write

1

In

Indicates write transaction 8

address

32

In

Address of the transaction

readdata

32, 64, 128, or 256

Out

Read data return

readdatavalid

1

Out

Indicates the readdata signal contains valid data in response to a previous read request.

writedata

32, 64, 128, or 256

In

Write data for a transaction

byteenable

4, 8, 16, 32

In

Byte enables for each write byte lane

waitrequest

1

Out

Indicates need for additional cycles to complete a transaction

burstcount

11

In

Transaction burst length. The value of the maximum burstcount parameter must be a power of 2.

The read and write interfaces are configured to the same size. The byte‑enable size scales with the data bus size.

8 The Avalon-MM protocol does not allow read and write transactions to be posted concurrently.

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