External Memory Interface Handbook Volume 3: Reference Material

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

5.1. Multi-Port Front End (MPFE)

The multi-port front end and its associated fabric interface provide up to six command ports, four read-data ports and four write-data ports, through which user logic can access the hard memory controller. Each port can be configured as read only or write only, or read and write ports may be combined to form bidirectional data ports. Ports can be 32, 64, 128, or 256 data bits wide, depending on the number of ports used and the type (unidirectional or bidirectional) of the port.

Fabric Interface

The fabric interface provides communication between the Avalon-ST-like internal protocol of the hard memory interface and the external Avalon-MM protocol. The fabric interface supports frequencies in the range of 10 MHz to one-half of the memory interface frequency. For example, for an interface running at 533 MHz, the maximum user logic frequency is 267 MHz. The MPFE handles the clock crossing between user logic and the hard memory interface.

The multi-port front end read and write FIFO depths are 8, and the command FIFO depth is 4. The FIFO depths are not configurable.

Operation Ordering

Requests arriving at a given port are executed in the order in which they are received.

Requests arriving at different ports have no guaranteed order of service, except when a first transaction has completed before the second arrives.

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