---
title: "Minimum SPI frequency"
url: "https://maker.wiznet.io/forum/14083"
markdown_url: "https://maker.wiznet.io/forum/14083/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "theJoel"
created: "2020-12-08T20:55:43+09:00"
last_activity: "2020-12-14T04:37:14+09:00"
language: "en"
views: 679
replies: 1
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# Minimum SPI frequency

## Question

Asked by theJoel on 2020-12-08 in Ethernet Chips.

Is there a recommended minimum SPI frequency to support the W6100 on a 100Mbit network?

I’d like to use MACRAW but it seems even if the Host MCU ran the SPI clock at 70Mhz (max) we will never keep up with 100Mb/s. Though it certainly depends on how busy the network is…

Is it ok to run the SPI bus at say 2 - 5 MHz and rely on the TCP windowing to slow down the remote device? If the Rx buffer remains full for a time does that mean no ARP or ICMP messages can be responded to?

Cheers,
+Joel.

## Replies

### Reply 1 by irina, 2020-12-14

Hi,

As far as I know, the minimum guaranteed speed of the SCLK is 33.3 MHz which was tested and measured with the stable waveform.
I think it would be good to refer to the picture below regarding SPI speed.

[![image](https://maker.wiznet.io/forum_uploads/wiznet/original/2X/6/6854ee3aadb2069c379b3b1c9caf56e58a2c9077.png) image678×627 17.7 KB](https://maker.wiznet.io/forum_uploads/wiznet/original/2X/6/6854ee3aadb2069c379b3b1c9caf56e58a2c9077.png)

![](https://avatars.discourse-cdn.com/v4/letter/t/c77e96/48.png) theJoel:

> If the Rx buffer remains full for a time does that mean no ARP or ICMP messages can be responded to?

If the RX buffer is full, wiznet chip can’t receive data.

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Source: https://maker.wiznet.io/forum/14083