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

The ULA reads a 6.14K pixel map and a 768-byte attribute map from the lower 16KB of RAM.

Use a Xilinx or Altera chip to recreate the ULA logic (see the project for schematics). Discrete Logic: Use 74-series chips (this results in a very large board). Microcontroller:

Use a real hardware Z80 processor alongside modern static RAM (SRAM). Pair them with a CPLD (Complex Programmable Logic Device) or an FPGA programmed to act exactly like the ULA.

If you want to apply the "ZX Design" philosophy to a modern retro portable computer, you must follow the same constraints that made the original Spectrum brilliant: component consolidation, clever memory architecture, and a compact footprint. The ULA reads a 6

The stands out as a model of modern accessibility. Based on the $4 Raspberry Pi Pico microcontroller (RP2040), it runs Fruit-Bat's ZX Spectrum emulator to deliver complete 48K/128K compatibility. The hardware consists of a custom PCB, a 2.8-inch IPS display, 49 tactile keyboard switches, a microSD card slot for game storage, and an 18650 lithium battery with USB-C charging. The result is a pocketable Speccy that fits in a jacket pocket—something no 1980s schoolchild could have imagined. An open-source variant, the ZX Spectrum Portable project by stormbytes1970, adds a laptop-style clamshell 3D-printed case and a 1500mAh battery delivering about two and a half hours of gameplay.

| Component | Example Model | |-----------|----------------| | CPU | Z84C0020PEC (Z80, 3.3V, 20MHz) | | ULA Replacement | Raspberry Pi Pico (RP2040) | | Display | 1.8" 128x160 SPI (or 2.0" 240x240) | | Battery | 802540 1000mAh LiPo | | Charger | TP4056 + protection | | Regulator | MCP1703-3302E | | Keyboard | 40x tactile switch matrix PCB | | Speaker | 8 ohm, 1W | | SD card slot | microSD push-push |

Use a real CMOS Z80 CPU running at 3.5MHz or 7MHz paired with your CPLD. This provides true hardware cycle-accuracy. System-on-Chip (SoC): Microcontrollers like the Raspberry Pi Pico (RP2040) Go to product viewer dialog for this item. Go to product viewer dialog for this item. Microcontroller: Use a real hardware Z80 processor alongside

The Spectrum keyboard used a simple matrix layout. The ULA mapped the keys across 8 address lines, allowing the CPU to read the state of multiple keys simultaneously using standard input/output (I/O) instructions. Designing a Modern Portable Microcomputer: Step-by-Step

Fully tactile 40-key matrix keyboard tailored for classic Sinclair keyword shortcuts.

Your FPGA code will mimic the exact internal logic gates of the 5C112 ULA, including the precise video timing states and memory contention delays. The stands out as a model of modern accessibility

This guide breaks down how the original ULA worked and provides a blueprint for replicating its behavior using modern hardware to build your own portable ZX Spectrum clone. Understanding the Sinclair ULA: The Heart of the Spectrum

If you are ready to start building your custom microcomputer, let me know:

Reading display data from RAM and converting it into television signals (Luma, Chroma, and sync).