---
title: "packet size detecting in W5100"
url: "https://maker.wiznet.io/forum/13175"
markdown_url: "https://maker.wiznet.io/forum/13175/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "FPGA Friend"
created: "2019-01-20T17:14:28+09:00"
last_activity: "2020-08-24T16:14:49+09:00"
language: "en"
views: 553
replies: 2
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# packet size detecting in W5100

## Question

Asked by FPGA Friend on 2019-01-20 in Ethernet Chips.

Hi
I’m using w5100 and want to know:
how to find the number of “packet” received? means: if 2 packet (with 100 byte data) received in w5100 and after that i go to read them, Sn_RX_RSR is 200? how to differentiate these two packets?

## Replies

### Reply 1 by Eugeny, 2019-01-20

![](https://avatars.discourse-cdn.com/v4/letter/f/898d66/48.png) FPGA_Friend:

> if 2 packet (with 100 byte data) received in w5100 and after that i go to read them, Sn_RX_RSR is 200

Yes.

![](https://avatars.discourse-cdn.com/v4/letter/f/898d66/48.png) FPGA_Friend:

> how to differentiate these two packets?

You do not need it for TCP connection, and this type of connection deliberately hides this information from session layer.

### Reply 2 by irina, 2020-05-25

I know it the register value can’t reset every time you receive a data packet.
Just it can modify the register value before socket open operate.

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Source: https://maker.wiznet.io/forum/13175