---
title: "H8 CP/NET WIZNET Network Controller"
url: "https://maker.wiznet.io/jaden/projects/h8-cp-net-wiznet-network-controller/"
markdown_url: "https://maker.wiznet.io/jaden/projects/h8-cp-net-wiznet-network-controller/md"
type: "UCC: User Created Content"
author: "Norberto"
author_url: "https://koyado.com/Heathkit/H8_CP_NET_SPI_Wiznet_Network.html"
editor: "WIZnet"
editor_url: "https://maker.wiznet.io/"
original_author: "Norberto"
original_url: "https://koyado.com/Heathkit/H8_CP_NET_SPI_Wiznet_Network.html"
published: "2025-09-16"
language: "en"
likes: 0
views: 1217
comments: 0
source: "WIZnet Makers (https://maker.wiznet.io/)"
---

# H8 CP/NET WIZNET Network Controller

> H8 CP/NET WIZNET Network Controller

Original author: Norberto (source: https://koyado.com/Heathkit/H8_CP_NET_SPI_Wiznet_Network.html)

## Article

## H8 CP/NET SPI WIZNET Network Card Overview

### What is this card used for?

![](https://maker.wiznet.io/upload/ckeditor5/447083523%5F1758732911%2Epng)

The **H8 CP/NET SPI WIZNET Network Card** is an **Ethernet expansion board** designed for the Heathkit **H8** retro computer.

It uses the **WIZnet WIZ850io module (based on the W5500 Ethernet controller)** to provide TCP/IP networking over an SPI interface.

Its main purpose is to enable **CP/NET networking** on the H8, allowing the machine to act as a CP/NET client and connect to a CP/NET server. Through this, the H8 can support **remote disk access, file transfers, and shared resources** just like in the CP/M era.

Documentation includes **schematics, GAL files, firmware, and CP/M3 disk images with network support**, making it a practical project for builders and enthusiasts.

### What is the Heathkit H8?

![](https://maker.wiznet.io/upload/ckeditor5/447083523%5F1758733036%2Epng)

The **Heathkit H8** was an **Intel 8080A-based 8-bit microcomputer kit** released in 1977.

It ran **CP/M** or Heath’s own **HDOS** operating system.

Unlike many contemporaries that used the S-100 bus, the H8 introduced its own **50-pin “Benton Harbor” bus**, forming the basis of the H8/H89 family of systems.

### Why WIZnet (W5500)?

![](https://maker.wiznet.io/upload/ckeditor5/447083523%5F1758733139%2Epng)

The **W5500** includes a built-in TCP/IP stack, which offloads protocol handling from the host CPU.

This makes it ideal for retro systems like the H8, where resources are limited but reliable Ethernet networking is desired.

The **WIZ850io module** integrates the W5500, transformer, and RJ-45 connector into a compact plug-in board, making it straightforward to connect via SPI.

Resource [Link](https://koyado.com/Heathkit/H8_CP_NET_SPI_Wiznet_Network.html)

![](https://maker.wiznet.io/upload/ckeditor5/447083523%5F1758733306%2Epng)

---

Source: https://maker.wiznet.io/jaden/projects/h8-cp-net-wiznet-network-controller/