---
title: "Spi full duplex problem"
url: "https://maker.wiznet.io/forum/14714"
markdown_url: "https://maker.wiznet.io/forum/14714/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "juan rodri"
created: "2022-11-19T02:52:20+09:00"
last_activity: "2022-11-19T08:40:33+09:00"
language: "en"
views: 493
replies: 1
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# Spi full duplex problem

## Question

Asked by juan rodri on 2022-11-19 in Ethernet Chips.

Hello,
Im working with stm8s003 and W5500. Im having problems with incoming data from W5500.

Pinout
Stm8 w5500
Miso---------miso
Mosi---------mosi
Clk------------clk
Cs-------------cs

Spi config
Fullduplex
Msbfirst
8mhz
Cpol=1
Cpha=1

With logic analizer i can see that mosi and miso are working, but i always sample 0xFF(if miso is pullup) and 0x00(if miso is pulldown) inside stm8 data register.
I have tried miso as floating also.
I have tried polling and interrupt spi.
I dont know if im doing something wrong.
Can W5500 works at 8mhz ? Must it works in full duplex mode?
Anyone has any tip?

Thanks in advance

## Replies

### Reply 1 by Eugeny, 2022-11-19

juan_rodri:

> Can W5500 works at 8mhz ?

Datasheet says 33.3 MHz.

juan_rodri:

> Must it works in full duplex mode?

Refer to the chapter 2.3 of the datasheet, it comprehensively shows what is going on the SPI bus. When master sends first 3 bytes for the command, W5500 responds with bytes 1, 2, and 3 - therefore it is full duplex, but “data” transferred during this phase is always the same and used for diagnostic purposes to identify if W5500 confirms reception of the command bytes.

juan_rodri:

> i always sample 0xFF(if miso is pullup) and 0x00(if miso is pulldown) inside stm8 data register

Suggests you sample at the wrong time.

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Source: https://maker.wiznet.io/forum/14714