HC 77B Bundle Overview
The HC-77B is the first publicly released HomeComp machine.
| Field | Detail |
|---|---|
| Machine | HC-77B |
| Launch context | Easter 1979 Complete System Bundle |
| Type | Front-panel single-board microcomputer |
| CPU | MOS Technology 6502 |
| Clock | 1 MHz |
| Primary interface | Front-panel display and keypad |
| Storage | Cassette interface |
| Release status | Publicly released |
The HC-77B launch release establishes the starting point for HomeComp Ecosystem Era 1.
HC-77B system board overview.
| Area | HC-77B Launch Specification |
|---|---|
| CPU | MOS Technology 6502 |
| Clock | 1 MHz |
| RAM | 1 KB Base + 3 KB expansion |
| ROM | Boot/monitor ROM included with the emulator release |
| BASIC | 8 KB ROM expansion included in bundle |
| Display | 8-digit seven-segment front-panel display |
| Input | Hexadecimal keypad with dedicated monitor keys |
| Cassette | Built-in cassette support in the emulator; blank tapes can be created |
| Keyboard expansion | Included in bundle |
| Video expansion | Included in bundle |
| Expansion model | External expansion/peripheral support through the HC-77B expansion API |
The HC-77B is a front-panel-first machine.
It is operated through its hexadecimal keypad and 8-digit seven-segment display. The monitor ROM provides the basic control environment: inspecting memory, entering data, viewing registers, starting execution, and using cassette load/save functions.
The HC-77B should not be understood as a BASIC-first home computer. It begins as a monitor-controlled 6502 system, with richer software and hardware capability appearing through later ecosystem releases and expansion hardware.
For machine-level operation, the included HC-77B User Manual PDF is authoritative.
This release provides a complete system with 4 KB total RAM, an 8K BASIC ROM, Display adaptor with RF connection to a dometic TV and an ASCII keyboard attachment.
The bundle is designed to give a complete usable home computer setup. It boots directly to the standard HC77 system ROM. For BASIC enter address $D000 and press GO.
The HC-77B uses a conventional 6502-style low-RAM, high-ROM arrangement.
| Address Range | Purpose | Notes |
|---|---|---|
$0000-$03FF |
Base RAM | 1 KB fitted in the launch machine |
$0400-$0FFF |
3K RAM Expansion | |
$1000-$EFFF |
General expansion space | Reserved for expansion ROM, RAM, or peripheral use |
$D000-$EFFF |
8K BASIC ROM | |
$F000-$F1FF |
Screen RAM for CRT Dispay | |
$F200-$F6FF |
Reserved I/O and expansion space | Video, keyboard, peripheral, and future device space |
$F700-$F7FF |
Base I/O | Core machine I/O region |
$F800-$FFFF |
Monitor ROM | Boot and monitor ROM |
This wiki gives only the high-level memory map. The included user manual and technical documents should be treated as the authoritative released documentation for detailed operation.
The HC-77B front panel provides the base machine interface.
| Component | Description |
|---|---|
| Display | 8-digit seven-segment LED display |
| Main input | Hexadecimal keypad |
| Function keys | Dedicated monitor-control keys |
| Operation style | Direct address/data/register interaction through the monitor ROM |
The front panel remains central even when optional launch expansions are present.
Cassette support is active in the emulator release.
The emulator provides cassette handling through the release's tapes/ folder and supports the creation of blank tapes.
The following system expansions available seperately:
- TTY Interface
- Scrolling LED Display
The details of using emulator extensions and peripheral examples are covered in the Expansion Bus API section.
The emulator release includes the authoritative HC-77B machine documentation in PDF form.
Useful repository files:
Use the included documentation for detailed machine operation, worked examples, and front-panel monitor behaviour. This wiki page is intended only as a public technical overview.