Embedded Peripherals IP User Guide

ID 683130
Date 12/13/2021
Public

A newer version of this document is available. Customers should click here to go to the newest version.

Document Table of Contents
1. Introduction 2. Avalon® -ST Multi-Channel Shared Memory FIFO Core 3. Avalon® -ST Single-Clock and Dual-Clock FIFO Cores 4. Avalon® -ST Serial Peripheral Interface Core 5. SPI Core 6. SPI Agent/JTAG to Avalon® Host Bridge Cores 7. Intel eSPI Agent Core 8. eSPI to LPC Bridge Core 9. Ethernet MDIO Core 10. Intel FPGA 16550 Compatible UART Core 11. UART Core 12. JTAG UART Core 13. Intel FPGA Avalon® Mailbox Core 14. Intel FPGA Avalon® Mutex Core 15. Intel FPGA Avalon® I2C (Host) Core 16. Intel FPGA I2C Agent to Avalon® -MM Host Bridge Core 17. Intel FPGA Avalon® Compact Flash Core 18. EPCS/EPCQA Serial Flash Controller Core 19. Intel FPGA Serial Flash Controller Core 20. Intel FPGA Serial Flash Controller II Core 21. Intel FPGA Generic QUAD SPI Controller Core 22. Intel FPGA Generic QUAD SPI Controller II Core 23. Interval Timer Core 24. Intel FPGA Avalon FIFO Memory Core 25. On-Chip Memory (RAM and ROM) Intel FPGA IP 26. On-Chip Memory II (RAM or ROM) Intel FPGA IP 27. Optrex 16207 LCD Controller Core 28. PIO Core 29. PLL Cores 30. DMA Controller Core 31. Modular Scatter-Gather DMA Core 32. Scatter-Gather DMA Controller Core 33. SDRAM Controller Core 34. Tri-State SDRAM Core 35. Video Sync Generator and Pixel Converter Cores 36. Intel FPGA Interrupt Latency Counter Core 37. Performance Counter Unit Core 38. Vectored Interrupt Controller Core 39. Avalon® -ST Data Pattern Generator and Checker Cores 40. Avalon® -ST Test Pattern Generator and Checker Cores 41. System ID Peripheral Core 42. Avalon® Packets to Transactions Converter Core 43. Avalon® -ST Multiplexer and Demultiplexer Cores 44. Avalon® -ST Bytes to Packets and Packets to Bytes Converter Cores 45. Avalon® -ST Delay Core 46. Avalon® -ST Round Robin Scheduler Core 47. Avalon® -ST Splitter Core 48. Avalon® -MM DDR Memory Half Rate Bridge Core 49. Intel FPGA GMII to RGMII Converter Core 50. Intel FPGA MII to RMII Converter Core 51. Intel FPGA HPS GMII to TSE 1000BASE-X/SGMII PCS Bridge Core 52. Intel FPGA HPS EMAC to Multi-rate PHY GMII Adapter Core 53. Intel FPGA MSI to GIC Generator Core

48.3. Functional Description

The Avalon® MM DDR Memory Half Rate Bridge works under two constraints:

  • Its memory-side host has a clock frequency that is synchronous (zero phase shift) to, and twice the frequency of, the CPU-side agent.
  • Its memory-side host is half as wide as its CPU-side agent.

The bridge leverages these two constraints to provide lightweight, low-latency clock-crossing logic between the CPU and the memory. These constraints are in contrast with the Avalon® -MM Clock-Crossing Bridge, which makes no assumptions about the frequency/phase relationship between the host- and agent-side clocks, and provides higher-latency logic that fully-synchronizes all signals that pass between the two domains.

The Avalon® MM DDR Memory Half-Rate Bridge has an Avalon® -MM agent interface that accepts single-word (non-bursting) transactions. When the agent interface receives a transaction from a connected CPU, it issues a two-word burst transaction on its host interface (which is half as wide and twice as fast). If the transaction is a read request, the bridge's host interface waits for the agent’s two-word response, concatenates the two words, and presents them as a single readdata word on its agent interface to the CPU. Every time the data width is halved, the clock rate is doubled. As a result, the data throughput is matched between the CPU and the off-chip memory device.

The figure below shows the latency in the Avalon® -MM Half-Rate Bridge core. The core adds two cycles of latency in the agent clock domain for read transactions. The first cycle is introduced during the command phase of the transaction and the second cycle, during the response phase of the transaction. The total latency is 2+<x>, where <x> refers to the latency of the DDR SDRAM high-performance memory controller. Using the clock crossing bridge for this same purpose would impose approximately 12 cycles of additional latency.

Figure 141.  Avalon® -MM DDR Memory Half-Rate Bridge Block Diagram