Low Latency 40G Ethernet Intel® FPGA IP User Guide: Agilex™ 5 FPGAs and SoCs

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ID 813652
Date 7/22/2024
Public
Document Table of Contents
Document Table of Contents x
1. About the Low Latency 40G Ethernet Intel® FPGA IP 2. Low Latency 40G Ethernet Intel® FPGA IP Parameters 3. Getting Started 4. Functional Description 5. Clocking and Reset Requirements 6. Interfaces and Signal Descriptions 7. Control, Status, and Statistics Register Descriptions 8. Comparison Between Various Low Latency 40G Ethernet Intel® FPGA IPs 9. Document Revision History for Low Latency 40G Ethernet Intel® FPGA IP User Guide: Agilex™ 5 FPGAs and SoCs
1. About the Low Latency 40G Ethernet Intel® FPGA IP x
1.1. Low Latency 40G Ethernet Intel® FPGA IP Supported Features 1.2. Low Latency 40G Ethernet Intel® FPGA IP Device Family and Speed Grade Support 1.3. Resource Utilization 1.4. Release Information
1.2. Low Latency 40G Ethernet Intel® FPGA IP Device Family and Speed Grade Support x
1.2.1. Low Latency 40G Ethernet Intel® FPGA IP Device Family Support 1.2.2. Low Latency 40G Ethernet Intel® FPGA IP Device Speed Grade Support
3. Getting Started x
3.1. Introduction to Intel® FPGA IP 3.2. Installing and Licensing Intel® FPGA IPs 3.3. Specifying the IP Parameters and Options 3.4. Simulating the IP 3.5. Generated File Structure 3.6. Integrating Your IP in Your Design 3.7. Testbench 3.8. Compiling the Full Design and Programming the FPGA
3.6. Integrating Your IP in Your Design x
3.6.1. Pin Assignments 3.6.2. Placement Settings
3.7. Testbench x
3.7.1. Understanding the Testbench Behavior
4. Functional Description x
4.1. Low Latency 40G Ethernet Intel® FPGA IP Functional Description 4.2. GTS Transceiver Configuration 4.3. TX MAC Datapath 4.4. RX MAC Datapath 4.5. Flow Control 4.6. Frame Status Checking 4.7. Link Fault Signaling Interface
4.3. TX MAC Datapath x
4.3.1. Preamble Pass-through/Insertion 4.3.2. Padding Bytes Insertion 4.3.3. Deficit Idle Count 4.3.4. TX CRC Insertion/Passthrough 4.3.5. TX Avalon® Streaming Filter 4.3.6. TX PCS 4.3.7. PMA
4.4. RX MAC Datapath x
4.4.1. RX Preamble Pass-through or Removal 4.4.2. RX CRC Checking and Dynamic Option to Forward 4.4.3. Strict SFD/Preamble Checking 4.4.4. RX PCS Functional Description
4.5. Flow Control x
4.5.1. TX Pause/PFC Flow Control Transmission 4.5.2. XON/XOFF Pause Frames
4.6. Frame Status Checking x
4.6.1. Frame Type Checking 4.6.2. Length Checking
5. Clocking and Reset Requirements x
5.1. Reset Requirements
6. Interfaces and Signal Descriptions x
6.1. TX MAC Interface to User Logic 6.2. RX MAC Interface to User Logic 6.3. GTS Transceivers Signals 6.4. GTS 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 6.10. GTS Reset Sequencer Intel® FPGA IP
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 7.5. Statistics Counters 7.6. Shadow Register
1. About the Low Latency 40G Ethernet Intel® FPGA IP
2. Low Latency 40G Ethernet Intel® FPGA IP Parameters
3. Getting Started
4. Functional Description
5. Clocking and Reset Requirements
6. Interfaces and Signal Descriptions
7. Control, Status, and Statistics Register Descriptions
8. Comparison Between Various Low Latency 40G Ethernet Intel® FPGA IPs
9. Document Revision History for Low Latency 40G Ethernet Intel® FPGA IP User Guide: Agilex™ 5 FPGAs and SoCs

3.7.1. Understanding the Testbench Behavior

The testbenches send traffic through the IP in transmit-to-receive loopback mode, exercising the transmit side and receive side of the IP in the same data flow. These testbenches send traffic to allow the Ethernet lanes to lock, and then send packets to the transmit client data interface and check the data as it returns through the receive client data interface.

The Low Latency 40G Ethernet Intel® FPGA IP for Agilex™ 5 devices implements virtual lanes as defined in the IEEE 802.3ba-2012 Ethernet Standard. The IP is fixed at four virtual lanes; the four virtual lanes are typically transmitted over four 10 Gbps physical lanes. When the lanes arrive at the receiver the lane streams are in an undefined order. Each lane carries a periodic PCS-VLANE alignment tag to restore the original ordering. The simulation establishes a random permutation of the physical lanes that is used for the remainder of the simulation.

Within each virtual lane stream, the data is 64B/66B encoded. Each word has two framing bits which are always either 01 or 10, never 00 or 11. The RX logic uses this pattern to lock onto the correct word boundaries in each serial stream. The process is probabilistic due to false locks on the pseudo-random scrambled stream.

Both the word lock and the alignment marker lock implement hysteresis as defined in the IEEE Standard for Ethernet, Section 4. Multiple successes are required to acquire lock and multiple failures are required to lose lock. The “fully locked” messages in the simulation log indicate the point at which a physical lane has successfully identified the word boundary and virtual lane assignment.

In the event of a catastrophic error, the RX PCS automatically attempts to reacquire alignment. The MAC properly identifies errors in the datastream.

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