40- and 100-Gbps Ethernet MAC and PHY MegaCore Function User Guide

ID 683114
Date 6/15/2022
Public
Document Table of Contents

3.2.12. Link Fault Signaling Interface

The 40‑100GbE IP core provides link fault signaling as defined in the IEEE 802.3ba-2010 100G Ethernet Standard . The 40GbE and 100GbE MAC include a Reconciliation Sublayer (RS) located between the MAC and the XLGMII or CGMII to manage local and remote faults. Link fault signaling on the Ethernet link is disabled by default but can be enabled by the Enable Link Fault Sequence register. When the LINK_FAULT_CONFIG register bits [1:0] have the value of 2'b01, link fault signaling is enabled in normal bidirectional mode. In this mode enabled, the local RS TX logic can transmit remote fault sequences in case of a local fault and can transmit IDLE control words in case of a remote fault. An additional configuration register (MAC/RS link fault sequence configuration) is provided to select the type of information to be transmitted in case of a local or remote fault. Using the configuration bits, you can send remote fault sequence ordered sets, IDLE control words, or regular traffic in the case of a local or remote fault.

The RS RX logic sets remote_fault_status or local_fault_status to 1 when the RS RX block receives remote fault or local fault sequence ordered sets. When valid data is received in more than 127 columns, the RS RX logic resets the relevant fault status (remote_fault_status or local_fault_status) to 0.

Figure 38. Link Fault Signaling Example

The IEEE standard specifies RS monitoring of RXC<7:0> and RXD<63:0> for Sequence ordered_sets. For more information, refer to Figure 81–9—Link Fault Signaling state diagram and Table 81-5—Sequence ordered_sets in the IEEE 802.3ba 2010 100G Ethernet Standard. The variable link_fault is set to indicate the value of an RX Sequence ordered_set when four fault_sequences containing the same fault value are received with fault sequences separated by less than 128 columns and with no intervening fault_sequences of different fault values. The variable link_fault is set to OK following any interval of 128 columns not containing a remote fault or local fault Sequence ordered_set.

Table 25.  Signals of the Link Fault Signaling Interface

Signal Name

Direction

Description

remote_fault_from_rx

Output

Asserted when remote fault is detected in RX MAC. Available in RX-only variations.

If link fault signaling is disabled, this signal is present but is tied low (always has the value of 0).

local_fault_from_rx

Output

Asserted when local fault is detected in RX MAC. Available in RX-only variations.

If link fault signaling is disabled, this signal is present but is tied low (always has the value of 0).

remote_fault_to_tx

Input

Input to the TX MAC. Asserted when remote fault is detected. Visible in TX-only variations and used internally in duplex IP core variations.

local_fault_to_tx

Input

Input to the TX MAC. Asserted when local fault is detected. Visible in TX-only variations and used internally in duplex IP core variations.

remote_fault_status

Output

Asserted when remote fault is detected in RX MAC in a duplex IP core variation. In duplex IP core variations, remote_fault_from_rx is connected internally to remote_fault_to_tx, and this signal is available externally as remote_fault_status.
local_fault_status

Output

Asserted when local fault is detected in RX MAC in a duplex IP core variation. In duplex IP core variations, local_fault_from_rx is connected internally to local_fault_to_tx, and this signal is available externally as local_fault_status.