To Design A Microcomputer Zx Design Retro Computer Portable | The Zx Spectrum Ula How

Replicate the original 8x5 switch matrix. The Z80 CPU reads this layout by setting specific address lines low and reading the data bus lines.

Recreating the ZX Spectrum as a portable, handheld retro computer is an excellent project for hardware hackers. Thanks to modern programmable silicon, you do not need to hunt down obsolete Ferranti chips. Step 1: Choosing Your Core Logic (FPGA vs. Microcontroller) To replicate the ULA, you have two primary options:

Sinclair Research revolutionized this by using a Ferranti . A ULA is a precursor to the modern FPGA—a chip with pre-fabricated logic gates that are wired together in the final manufacturing stages according to a custom design mask. The ZX Spectrum ULA combined several critical systems into one 40-pin package:

In the early 1980s, building a microcomputer required dozens of individual logic chips (TTL chips) to handle video generation, cassette input/output, keyboard scanning, and memory management. This made computers bulky, power-hungry, and expensive. Replicate the original 8x5 switch matrix

Before manufacturing your custom portable microcomputer, cross-reference your design against this final specification checklist:

You can replicate the ULA's functions using standard, off-the-shelf logic chips.

Operating at 7MHz, it outputs 256 horizontal pixels per active line. Thanks to modern programmable silicon, you do not

For a modern retro-build or portable device, you can replace the original ULA using these methods: ZX MAX 128 ZX Spectrum Clone Build

The classic Spectrum keyboard is a membrane matrix that feels uniquely rubbery. For a modern portable computer:

Designing a modern microcomputer based on the ZX Spectrum requires a deep understanding of its custom "heart": the Ferranti Uncommitted Logic Array (ULA) A ULA is a precursor to the modern

The CPU has 16 address lines (A0–A15) that can address 64KB of memory. You cannot just wire the CPU directly to the chips. You need decoding logic to tell the chips which address range they should listen to.

In those days, most computers were a mess of dozens of tiny chips. But the Spectrum was different. The

The ULA is directly responsible for reading the Spectrum's unique screen memory layout and outputting a television-compatible video signal (PAL or NTSC).