---
title: "Under what condition(s) is PHYCFGR-LNK set to 'Link Up'?"
url: "https://maker.wiznet.io/forum/13489"
markdown_url: "https://maker.wiznet.io/forum/13489/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "Mxyxixptlick"
created: "2019-09-23T01:28:03+09:00"
last_activity: "2019-09-24T08:48:14+09:00"
language: "en"
views: 600
replies: 3
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# Under what condition(s) is PHYCFGR-LNK set to 'Link Up'?

## Question

Asked by Mxyxixptlick on 2019-09-23 in Ethernet Chips.

I’ve always assumed it means that a physical network connection is present, but searching the manual today made me realize that I don’t really know that for sure. Does anyone know for certain under what conditions this bit is set and reset?

## Replies

### Reply 1 by Eugeny, 2019-09-23

Mxyxixptlick:

> but searching the manual today made me realize that I don’t really know that for sure

What exactly have you made thinking this way? In my opinion it must get set when carrier signal is detected.

### Reply 2 by Mxyxixptlick, 2019-09-23 (in reply to reply 1)

I was going to answer a question about a W5x00 Ethernet library that was posted at [Ethernet cable is not connected · Issue #111 · arduino-libraries/Ethernet · GitHub](https://github.com/arduino-libraries/Ethernet/issues/111) but realized I didn’t have a definitive answer.

Your answer makes sense, but I’m hoping someone from Wiznet can confirm that’s how it works.

### Reply 3 by irina, 2019-09-24

Hi~
LNK bit of PHYCFGR operates same the link pin of W5500.
It is driven low whenever the PHY detects a valid link. We don’t know about valid link or any carrier signal because it operates internal to the PHY.

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Source: https://maker.wiznet.io/forum/13489