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

6144 bytes holding a resolution of 256 x 192 pixels.

To turn a desktop design into a handheld "Spectrum Pocket," focus on these specs: Use a 3.5" or 5" SPI TFT display

An FPGA (e.g., Lattice iCE40 UP5K or Sipeed Tang Nano) can replicate the ULA’s parallel logic exactly. 6144 bytes holding a resolution of 256 x 192 pixels

To design a microcomputer using a ULA, you'll need to understand the basics of digital logic, computer architecture, and integrated circuit design. Here's a step-by-step guide to get you started:

Like any complex chip, the first version of the ULA had a flaw. It didn’t always scan the keyboard correctly, causing missed keystrokes. Sinclair’s solution is a legendary piece of retro computing trivia: they soldered a small secondary circuit board (nicknamed the "Dead Cockroach") upside down next to the CPU to fix the timing signal. Here's a step-by-step guide to get you started:

To make further progress on your retro microcomputer design, let me know:

Small 3.5-inch TFT LCD screens can be driven directly via SPI or parallel interfaces from your microcontroller. To make further progress on your retro microcomputer

If you want true hardware-level accuracy, an FPGA (like the Spartan-6 or Cyclone IV) allows you to recreate the actual digital logic circuits of the Z80 and the ULA. Devices like the ZX Uno or the ZX Spectrum Next use this method.

Inside the ZX Spectrum ULA: Designing a Custom Microcomputer Heart

Select Your ProcessorWhile the Zilog Z80 is still in production, many designers use the Z80 CMOS version for lower power consumption in portable builds. Alternatively, an ESP32 or Raspberry Pi Pico can emulate the Z80 instruction set with ease.

By building your own portable microcomputer around these classic principles, you gain a deep appreciation for low-level system architecture while creating a piece of functional, pocket-sized nostalgia.