Low Latency E-Tile 40G Ethernet Intel® FPGA IP User Guide

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ID 683486
Date 7/12/2024
Public
Document Table of Contents
Document Table of Contents x
1. About the Low Latency E-Tile 40G Ethernet Intel® FPGA IP 2. Low Latency E-Tile 40G Ethernet IP Core Parameters 3. Getting Started 4. Functional Description 5. Reset 6. Interfaces and Signal Descriptions 7. Control, Status, and Statistics Register Descriptions 8. Debugging the Link 9. Ethernet Toolkit Overview 10. Low Latency E-Tile 40G Ethernet Intel® FPGA IP User Guide Archives 11. Comparison Between Low Latency E-Tile 40G Ethernet Core and Low Latency 40GbE IP Core 12. Document Revision History for Low Latency E-Tile 40G Ethernet Intel® FPGA IP User Guide
1. About the Low Latency E-Tile 40G Ethernet Intel® FPGA IP x
1.1. Release Information 1.2. Low Latency E-Tile 40G Ethernet Intel® FPGA IP Supported Features 1.3. Low Latency E-Tile 40G Ethernet Intel® FPGA IP Device Family and Speed Grade Support 1.4. Resource Utilization
1.3. Low Latency E-Tile 40G Ethernet Intel® FPGA IP Device Family and Speed Grade Support x
1.3.1. Device Family Support 1.3.2. Low Latency E-Tile 40G Ethernet Intel® FPGA IP Device Speed Grade Support
3. Getting Started x
3.1. Installing and Licensing Intel® FPGA IP Cores 3.2. Specifying the Low Latency E-Tile 40G Ethernet IP Core Parameters and Options 3.3. Simulating the IP Core 3.4. Generated File Structure 3.5. Integrating Your IP Core in Your Design 3.6. Low Latency E-Tile 40G Ethernet IP Core Testbench 3.7. Compiling the Full Design and Programming the FPGA
3.5. Integrating Your IP Core in Your Design x
3.5.1. Pin Assignments 3.5.2. Ethernet Adaptation Flow 3.5.3. Placement Settings for the Low Latency E-Tile 40G Ethernet Core
3.6. Low Latency E-Tile 40G Ethernet IP Core Testbench x
3.6.1. Understanding the Testbench Behavior
4. Functional Description x
4.1. Low Latency E-Tile 40G Ethernet Core Functional Description 4.2. User Interface to Ethernet Transmission
4.1. Low Latency E-Tile 40G Ethernet Core Functional Description x
4.1.1. Low Latency E-Tile 40G Ethernet Core TX MAC Datapath 4.1.2. Low Latency E-Tile 40G Ethernet Core RX MAC Datapath 4.1.3. Link Fault Signaling Interface 4.1.4. Flow Control
4.1.1. Low Latency E-Tile 40G Ethernet Core TX MAC Datapath x
4.1.1.1. Frame Padding 4.1.1.2. Preamble Insertion 4.1.1.3. Inter-Packet Gap Generation and Insertion 4.1.1.4. Frame Check Sequence (CRC-32) Insertion
4.1.2. Low Latency E-Tile 40G Ethernet Core RX MAC Datapath x
4.1.2.1. IP Core Preamble Processing 4.1.2.2. IP Core Strict SFD Checking 4.1.2.3. Length/Type Field Processing 4.1.2.4. RX CRC Checking and Dynamic Forwarding
4.1.2.3. Length/Type Field Processing x
4.1.2.3.1. Length Checking
4.1.4. Flow Control x
4.1.4.1. TX Pause/PFC Flow Control Transmission 4.1.4.2. XON/XOFF Pause Frames
4.2. User Interface to Ethernet Transmission x
4.2.1. Order of Transmission 4.2.2. Bit Order For TX and RX Datapaths
6. Interfaces and Signal Descriptions x
6.1. TX MAC Interface to User Logic 6.2. RX MAC Interface to User Logic 6.3. Transceivers Signals 6.4. Transceiver Reconfiguration Signals 6.5. Avalon® Memory-Mapped Management Interface 6.6. Miscellaneous Status and Debug Signals 6.7. Reset Signals 6.8. Clocks 6.9. Flow Control Interface
7. Control, Status, and Statistics Register Descriptions x
7.1. PHY Registers 7.2. TX MAC Registers 7.3. RX MAC Registers 7.4. Pause/PFC Flow Control Registers
9. Ethernet Toolkit Overview x
9.1. Features
1. About the Low Latency E-Tile 40G Ethernet Intel® FPGA IP
2. Low Latency E-Tile 40G Ethernet IP Core Parameters
3. Getting Started
4. Functional Description
5. Reset
6. Interfaces and Signal Descriptions
7. Control, Status, and Statistics Register Descriptions
8. Debugging the Link
9. Ethernet Toolkit Overview
10. Low Latency E-Tile 40G Ethernet Intel® FPGA IP User Guide Archives
11. Comparison Between Low Latency E-Tile 40G Ethernet Core and Low Latency 40GbE IP Core
12. Document Revision History for Low Latency E-Tile 40G Ethernet Intel® FPGA IP User Guide

4.1.4. Flow Control

Flow control reduces congestion at the local or remote link partner. When either link partner experiences congestion, the respective transmit control sends pause frames. XOFF Pause frames stop the remote transmitter. XON Pause frames let the remote transmitter resume data transmission. Flow control supports both Pause and Priority Flow Control (PFC) control frames:
  • IEEE 802.3 flow control—implements the IEEE 802.3 Annex 31B standard to manage congestion. This flow control is a mechanism to manage congestion at the local or remote partner. When the receiving device experiences congestion, it sends an XOFF pause frame to the emitting device to instruct the emitting device to stop sending data for a duration specified by the congested receiver. Data transmission resumes when the emitting device receives an XON pause frame (pause quanta = zero) or when the timer expires.
  • Priority-based flow control (PFC)—implements the IEEE 802.1Qbb standard. PFC manages congestion based on priority levels. It supports up to 8 priority queues. When the receiving device experiences congestion on a priority queue, it sends a PFC frame requesting the emitting device to stop transmission on the priority queue for a duration specified by the congested receiver. When the receiving device is ready to receive transmission on the priority queue again, it sends a PFC frame instructing the emitting device to resume transmission on the priority queue.
Figure 8. Flow Control Module Conceptual OverviewThe flow control module acts as a buffer between client logic and the TX and RX MAC.

Flow Control includes the following features:

  • Pause or PFC frame generation and transmission:
    • Configurable selection of standard or priority-based flow control
    • Programmable 1- or 2-bit XON/XOFF request mode
    • In 2-bit request mode, programmable selection of register or signal-based control
    • Programmable per-queue XOFF frame separation
    • Programmable destination and source addresses in outgoing pause and PFC frames
    • Programmable pause and PFC quanta
  • Client versus Pause or PFC frame transmission based on a priority-based arbitration scheme with frame-type indication for external downstream logic
  • Stopping the next client frame transmission on the reception of a valid Pause frame
  • Stopping the per queue client frame transmission on the reception of a valid PFC frame from the client. Includes per-queue PFC Pause quanta duration indicator
  • Pause or PFC frame reception and decode:
    • Programmable destination address for filtering incoming pause and PFC frames
    • Configurable Pause or PFC per-queue enable, directing the IP core to ignore incoming pause frames on disabled queues
    • Per-queue client frame transmission pause duration indicator

Section Content
TX Pause/PFC Flow Control Transmission
XON/XOFF Pause Frames

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