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AR# 17434

LogiCORE Gigabit Ethernet MAC v3.0 - "Link Status" is incorrectly reported in status register 1.2 with Auto-Negotiation disabled

Description

Keywords: COREGen, Gigabit, ethernet, MAC, auto negotiation, 1000BASE-X, PCS, PMA, synchronization, FIP3, FIP_3

Urgency: Standard

General Description:
When Auto-Negotiation is disabled on the Gigabit Ethernet MAC v3.0 core, the core never reports that it has lost receiver synchronization, even when the optical fiber is unplugged from the input of my design. Status register 1.2, "Link Status" (see table 26, page 49, in the v3.0 product data sheet) of the PCS sub-layer register is responsible for this information. This problem occurs only when Auto-Negotiation is built into the core and when it is disabled from the PCS configuration register. When Auto-Negotiation is enabled, the status register always reports the correct information.

Solution

The receiver's synchronization state machine will behave correctly. That is, it loses synchronization when the fiber is pulled out and regains synchronization when the fiber is replaced. However, when Auto-Negotiation is disabled, the actual state of the link is not correctly reported in status register bit 1.2, "Link Status." This register bit incorrectly reports that the Link Status is "UP."

To resolve this issue, apply the patch found in the Release Notes for the Gigabit Ethernet MAC v3.0 core, (Xilinx Answer 17129).
AR# 17434
Date Created 06/12/2003
Last Updated 08/31/2006
Status Archive
Type General Article