The Zx Spectrum Ula How To Design A Microcomputer Zx Design Retro Computer Portable ((new)) Jun 2026

6144 bytes holding a resolution of 256 x 192 pixels.

Pixel data was stored in a 6.12 KB block of video RAM, representing a 256x192 resolution.

The Sinclair ZX Spectrum remains one of the most iconic microcomputers of the 1980s. While its rubber keys and distinctive rainbow stripe are globally recognized, the true magic of the machine lay hidden inside its casing: the Uncommitted Logic Array (ULA). 6144 bytes holding a resolution of 256 x 192 pixels

To capture the ZX soul, you must implement the "Attribute Clash": Resolution: 256 x 192 pixels. 8 colors (with two brightness levels).

+-------------------------------------------------------+ | PORTABLE MICROCOMPUTER | | | | +-------------------+ +---------------------+ | | | Z80 CPU | | FPGA / CPLD (ULA) | | | | (Physical/Core) |<=====>| - Video Generation | | | +-------------------+ | - Keyboard Matrix | | | | - Contention Logic | | | +-------------------+ +----------+----------+ | | | SRAM / ROM | | | | | (System RAM) |<-----------------+ | | +-------------------+ v | | +---------------------+ | | +-------------------+ | TFT/LCD DISPLAY | | | | Li-ion Battery & | | (RGB/SPI Drive) | | | | Power Management | +---------------------+ | | +-------------------+ | +-------------------------------------------------------+ Step 1: Choosing Your Core Processing Unit You have two primary routes for the CPU: While its rubber keys and distinctive rainbow stripe

Implement a state machine that pulls the Z80 WAIT pin low if the CPU addresses memory between $4000 and $7FFF during the active display window. Step 3: Resolving Display Portability

The original Spectrum allocated the memory block from 0x4000 to 0x5AFF for the display file. preserve this limitation exactly.

If using an FPGA, driving a panel via a raw parallel RGB interface ensures zero latency and liquid-smooth 50Hz/60Hz refresh rates. Step 3: Replicating Keyboards and I/O

The original ULA outputted an RF or composite video signal meant for 1980s cathode-ray tube (CRT) televisions. For a portable build, you must modernize the output:

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

Design Note: When engineering your video rendering block, preserve this limitation exactly. Removing attribute clash destroys the retro accuracy and breaks specific graphical tricks engine coders used to bypass it. Dealing with Memory Contention