F-Tile 25G Ethernet Intel® FPGA IP User Guide

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ID 750198
Date 2/09/2023
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Document Table of Contents
Document Table of Contents x
1. About the F-Tile 25G Ethernet Intel FPGA IP User Guide 2. About this IP 3. Getting Started 4. F-tile 25G Ethernet Intel FPGA IP Parameters 5. Functional Description 6. Reset 7. Interfaces and Signal Descriptions 8. Control, Status, and Statistics Register Descriptions 9. Document Revision History for the F-tile 25G Ethernet Intel® FPGA IP User Guide
2. About this IP x
2.1. Release Information 2.2. Features 2.3. Device Family Support 2.4. Performance and Resource Utilization
3. Getting Started x
3.1. Installing and Licensing Intel® FPGA IP Cores 3.2. Specifying the 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. Compiling the Full Design and Programming the FPGA
3.1. Installing and Licensing Intel® FPGA IP Cores x
3.1.1. Intel® FPGA IP Evaluation Mode
3.5. Integrating Your IP Core in Your Design x
3.5.1. Pin Assignments 3.5.2. Adding the F-tile Reference and System PLL Clocks Intel® FPGA IP 3.5.3. Placement Settings for the 25G Ethernet Intel FPGA IP Core
5. Functional Description x
5.1. F-tile 25G Ethernet Intel FPGA IP Core Functional Description 5.2. User Interface to Ethernet Transmission
5.1. F-tile 25G Ethernet Intel FPGA IP Core Functional Description x
5.1.1. F-tile 25G Ethernet Intel FPGA IP TX MAC Datapath 5.1.2. 25 GbE TX PCS 5.1.3. F-tile 25G Ethernet Intel FPGA IP Core RX MAC Datapath 5.1.4. Link Fault Signaling Interface Local Fault (LF) Remote Fault (RF) Link Status Signals 5.1.5. 25 GbE RX PCS 5.1.6. Flow Control
5.1.1. F-tile 25G Ethernet Intel FPGA IP TX MAC Datapath x
5.1.1.1. Frame Padding 5.1.1.2. Preamble Insertion 5.1.1.3. Inter-Packet Gap Generation and Insertion 5.1.1.4. Frame Check Sequence (CRC32) Insertion
5.1.3. F-tile 25G Ethernet Intel FPGA IP Core RX MAC Datapath x
5.1.3.1. IP Core Preamble Processing 5.1.3.2. IP Core Malformed Packet Handling 5.1.3.3. Length/Type Field Processing
5.1.3.3. Length/Type Field Processing x
5.1.3.3.1. Length Checking 5.1.3.3.2. RX CRC Checking and Dynamic Forwarding
5.1.6. Flow Control x
5.1.6.1. TX Pause/PFC Flow Control Frame Transmission Request 5.1.6.2. XON/XOFF Pause Frames
5.2. User Interface to Ethernet Transmission x
5.2.1. Order of Transmission 5.2.2. Bit Order For TX and RX Datapaths
7. Interfaces and Signal Descriptions x
7.1. TX MAC Interface to User Logic 7.2. RX MAC Interface to User Logic 7.3. Transceivers 7.4. Transceiver Reconfiguration Signals 7.5. Avalon® Memory-Mapped Management Interface 7.6. Miscellaneous Status and Debug Signals 7.7. Clock Signals 7.8. Reset Signals
8. Control, Status, and Statistics Register Descriptions x
8.1. TX MAC Registers 8.2. RX MAC Registers 8.3. Pause/PFC Flow Control Registers 8.4. Statistics Registers 8.5. Hard IP Registers
8.4. Statistics Registers x
8.4.1. TX Statistics Registers 8.4.2. RX Statistics Registers
1. About the F-Tile 25G Ethernet Intel FPGA IP User Guide
2. About this IP
3. Getting Started
4. F-tile 25G Ethernet Intel FPGA IP Parameters
5. Functional Description
6. Reset
7. Interfaces and Signal Descriptions
8. Control, Status, and Statistics Register Descriptions
9. Document Revision History for the F-tile 25G Ethernet Intel® FPGA IP User Guide

5.1.4. Link Fault Signaling Interface

Link fault signaling reflects the health of the link. It operates between the remote Ethernet device Reconciliation Sublayer (RS) and the local Ethernet device RS. The link fault modules communicate status during the interframe period.

You enable link fault signaling by turning on Enable link fault generation in the parameter editor. For bidirectional fault signaling, the IP core implements the functionality defined in the IEEE 802.3ba 10G Ethernet Standard and Clause 46 based on the LINK_FAULT configuration register settings.

For unidirectional fault signaling, the core implements Clause 66 of the IEEE 802.3-2012 Ethernet Standard.
Figure 13. Link Fault Block Diagram

Local Fault (LF)

If an Ethernet PHY sublayer detects a fault that makes the link unreliable, it notifies the RS of the local fault condition. If unidirectional is not enabled, the core follows Clause 46. The RS stops sending MAC data, and continuously generates a remote fault status on the TX datapath. After a local fault is detected, the RX PCS modifies the MII data and control to send local fault sequence ordered sets. Refer to Link Fault Signaling Based On Configuration and Status below.

The RX PCS cannot recognize the link fault under the following conditions:

  • The RX PCS is not fully aligned.
  • The bit error rate (BER) is high.

Remote Fault (RF)

If unidirectional is not enabled, the core follows Clause 46. If the RS receives a remote fault status, the TX datapath stops sending MAC data and continuously generates idle control characters. If the RS stops receiving fault status messages, it returns to normal operation, sending MAC client data. Refer to Link Fault Signaling Based On Configuration and Status below.

Link Status Signals

The MAC RX generates two link fault signals: local_fault_status and remote_fault_status.
Note: These signals are real time status signals that reflect the status of the link regardless of the settings in the link fault configuration register.
This register is generated only if you turn on Enable link fault generation. The MAC TX interface uses the link fault status signals for additional link fault signaling.
Table 10.  Link Fault Signaling Based On Configuration and StatusFor more information about the LINK_FAULT register, refer to TX MAC Registers.
LINK_FAULT Register (0x405) Real Time Link Status Configured TX Behavior Comment
Bit [0] Bit [3] Bit [1] Bit [2]

LF Received

RF Received

TX Data

TX RF

1'b0 Don't care Don't care Don't care Don’t care Don’t care On Off

Disable Link fault signaling on TX.

RX still reports link status.

TX side Link fault signaling disabled on the link.

TX data and idle.
1'b1 1'b1 Don't care Don't care Don't care Don't care Off On

Force RF.

TX: Stop data. Transmit RF only
1'b1 1'b0 1'b1 1'b1 Don't care Don't care On Off

Unidir: Backwards compatible.

TX: Transmit data and idle. No RF.
1'b1 1'b0 1'b1 1'b0 1'b1 1'b0 On On

Unidir: LF received.

TX: Transmit data 1 column IDLE after end of packet and RF
1'b1 1'b0 1'b1 1'b0 1'b0 1'b1 On Off

Unidir: RF receives

TX: Transmit data and idle. No RF.
1'b1 1'b0 1'b1 1'b0 1'b0 1'b0 On Off

Unidir: No link fault

TX: Transmit data and idle. No RF.
1'b1 1'b0 1'b0 Don't care 1'b1 1'b0 Off On

Bidir: LF received

TX: Stop data. Transmit RF only.
1'b1 1'b0 1'b0 Don't care 1'b0 1'b1 Off Off

Bidir: RF received

TX: Stop data. Idle only. No RF.
1'b1 1'b0 1'b0 Don’t care 1'b0 1'b0 On Off

Bidir: No link fault

TX: Transmit data and idle. No RF.

At this time, the F-tile 25G Ethernet Intel FPGA IP core does not recognize received non-zero 4-bit ordered set types as an error.

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