External Memory Interface Handbook Volume 1: Intel® FPGA Memory Solution Introduction and Design Flow: For UniPHY-based Device Families

Download PDF
ID 710283
Date 3/06/2023
Public
Document Table of Contents
Document Table of Contents x
1. Introduction to this Handbook 2. Recommended Design Flow 3. Selecting Your Memory 4. Selecting Your FPGA Device
1. Introduction to this Handbook x
1.1. Introduction to Memory Solutions 1.2. Protocol Support Matrix 1.3. Document Revision History
2. Recommended Design Flow x
2.1. Getting Started With External Memory Interfaces 2.2. Document Revision History
2.1. Getting Started With External Memory Interfaces x
2.1.1. Selecting Your External Memory Device 2.1.2. Selecting Your FPGA 2.1.3. Planning Your Pin Requirements 2.1.4. Planning Your FPGA Resources 2.1.5. Determining Your Board Layout 2.1.6. Specifying Parameters for Your External Memory Interface 2.1.7. Performing Functional Simulation 2.1.8. Adding Design Constraints 2.1.9. Compiling Your Design and Verifying Timing 2.1.10. Verifying and Debugging External Memory Interface Operation
3. Selecting Your Memory x
3.1. DDR SDRAM Features 3.2. DDR2 SDRAM Features 3.3. DDR3 SDRAM Features 3.4. QDR, QDR II, and QDR II+ SRAM Features 3.5. RLDRAM II and RLDRAM 3 Features 3.6. LPDDR2 Features 3.7. Memory Selection 3.8. Example of High-Speed Memory in Embedded Processor 3.9. Example of High-Speed Memory in Telecom 3.10. Document Revision History
4. Selecting Your FPGA Device x
4.1. Memory Standards 4.2. I/O Interfaces 4.3. Wraparound Interfaces 4.4. Read and Write Leveling 4.5. Dynamic OCT 4.6. Device Settings Selection 4.7. Document Revision History
4.6. Device Settings Selection x
4.6.1. Device Speed Grade 4.6.2. Device Operating Temperature 4.6.3. Device Package Size 4.6.4. Device Density and I/O Pin Counts
1. Introduction to this Handbook
2. Recommended Design Flow
3. Selecting Your Memory
4. Selecting Your FPGA Device

3.8. Example of High-Speed Memory in Embedded Processor

In embedded processor applications—any system that uses processors, excluding desktop processors—due to its very low cost, high density, and low power, DDR SDRAM is typically used for main memory.

Next-generation processors invest a large amount of die area to on-chip cache memory to prevent the execution pipelines from sitting idle. Unfortunately, these on-chip caches are limited in size, as a balance of performance, cost, and power must be taken into consideration. In many systems, external memories are used to add another level of cache. In high-performance systems, three levels of cache memory is common: level one (8 Kbytes is common) and level two (512 Kbytes) on chip, and level three off chip (2 Mbytes).

High-end servers, routers, and even video game systems are examples of high‑performance embedded products that require memory architectures that are both high speed and low latency. Advanced memory controllers are required to manage transactions between embedded processors and their memories. Intel® Arria® series and Intel® Stratix® series FPGAs optimally implement advanced memory controllers by utilizing their built-in DQS (strobe) phase shift circuitry. The following figure highlights some of the features available in an Intel® FPGA in an embedded application, where DDR2 SDRAM is used as the main memory and QDR II/II+ SRAM or RLDRAM II/3 is an external cache level.

Figure 4. Memory Controller Example Using FPGA


One of the target markets of RLDRAM II/3 and QDR/QDR II SRAM is external cache memory. RLDRAM II and RLDRAM 3 have a read latency close to synchronous SRAM, but with the density of SDRAM. A sixteen times increase in external cache density is achievable with one RLDRAM II/3 versus that of synchronous static RAM (SSRAM). In contrast, consider QDR and QDR II SRAM for systems that require high bandwidth and minimal latency. Architecturally, the dual‑port nature of QDR and QDR II SRAM allows cache controllers to handle read data and instruction fetches completely independent of writes.

Level Two Title