---
title: "Question on FCS"
url: "https://maker.wiznet.io/forum/14267"
markdown_url: "https://maker.wiznet.io/forum/14267/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "mikesixes"
created: "2021-06-17T00:04:34+09:00"
last_activity: "2021-06-17T00:04:34+09:00"
language: "en"
views: 334
replies: 0
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# Question on FCS

## Question

Asked by mikesixes on 2021-06-17 in Ethernet Chips.

Using a W5100s in MACRAW mode, what happens when a packet is received with a bad frame check sequence? Is it rejected, and if so, is there any way to tell that a packet has been rejected? While I’m on the subject, does the W5100s append a FCS when it puts the packet out?

---

Source: https://maker.wiznet.io/forum/14267