The Zx Spectrum Ula How To Design A Microcomputer Zx Design Retro Computer Portable ((link))

Key Technical Insights

The ZX Spectrum ULA: How to Design a Microcomputer by Chris Smith is widely considered the definitive technical resource for understanding the "heart" of the Sinclair ZX Spectrum. Through painstaking reverse-engineering down to the transistor level, Smith reveals how a single custom chip—the Ferranti Uncommitted Logic Array (ULA)—managed almost all of the computer's operations, from video generation to keyboard scanning.

Designing a Microcomputer with a ULA

• Composite video (NTSC/PAL) via DAC or resistor ladder.
• HDMI output via small HDMI encoder (e.g., use FPGA with TMDS output or route through a small HDMI bridge IC).
• RGB/SCART or VGA via simple DACs for crisp output.

1. Download the "ZX Spectrum ULA reverse-engineered" logic diagrams (available on GitHub).
2. Buy a cheap FPGA dev board (e.g., Sipeed Tang Nano 20K).
3. Port the open-source ULA core to your board, driving a small LCD.
4. Design a PCB integrating a Z80 soft-core, SRAM, and SD card.
5. Print a case and load Jet Set Willy.

In the early 1980s, Richard Altwasser and the Sinclair team faced a challenge: build a color computer for under £100. Their solution was the Ferranti ULA, a "gate array" precursor to modern FPGAs. The ULA performed four critical roles: Key Technical Insights The ZX Spectrum ULA: How

10) Resources & inspiration