Color is applied in 8x8 pixel blocks. This "limitation" defines the retro aesthetic. 🔋 Making it Portable
The 40-pin ULA (specifically the 6C001E-7 in the Issue 2 board) performs five critical functions that define :
The original ULA halted the CPU whenever both tried to access the bottom 16KB of RAM at the same time (screen drawing took priority). In a modern design, you can eliminate this bottleneck entirely by using fast chips. SRAM is fast enough to allow dual-porting or interleaved access, meaning your display won't slow down your processor. 4. Going Portable: Display and Power
+-----------------------------------------------------------------------+ | PORTABLE RETRO SYSTEM | | | | +-------------------+ System Bus +------------------------+ | | | Z80 CPU |<==================>| MODERN ULA | | | | (Physical or Core) | | (FPGA / Microcontroller) | | | +-------------------+ +------------------------+ | | || || | | \/ \/ | | +---------+ +----------+ | | | RGB/LCD | | Keyboard | | | | Display | | Matrix | | | +---------+ +----------+ | +-----------------------------------------------------------------------+ Option A: The FPGA Approach (Hardware-Level Recreation) Color is applied in 8x8 pixel blocks
Replacing a faulty original ULA or building a system from scratch is best achieved via programmable logic. Chris Smith's landmark book, The ZX Spectrum ULA: How to Design a Microcomputer , reverse-engineered the exact schematic of the chip. You can implement this logic using: Xilinx XC95144XL CPLD Go to product viewer dialog for this item.
It managed the tape interface, speaker, and the 40-key matrix. 🛠️ How to Design a Modern "ZX-Style" Microcomputer
I'll search for information on the ZX Spectrum ULA, its architecture, how to design a microcomputer, and portable Spectrum projects. I'll use multiple search terms to cover different aspects. search results provide a good starting point. Result 0 looks like a book titled "The ZX Spectrum ULA: How to Design a Microcomputer" which seems highly relevant. I'll open it to get more details. Result 5 is a blog post about the ZX Spectrum. Result 6 is about ULA implementation. Result 2 shows clone designs. Result 3 and 7 show portable builds. Result 4 covers FPGA replacements. Result 5 covers ULAX. Result 6 covers ZX Spectrum Next. I'll open these to gather more detailed information. have gathered information from various sources. The book "The ZX Spectrum ULA: How to Design a Microcomputer" is a key resource. I also have details about the ULA's functions, clone designs, and portable projects. Now I need to synthesize this into a long article. The article should cover the ULA's role, the process of designing a microcomputer, and how to build a portable retro computer. I'll structure it with an introduction, sections on ULA, design principles, clone projects, portable builds, and a conclusion. I'll cite relevant sources. have gathered substantial information. The article will be structured into nine sections: Introduction, ULA as the heart of the ZX Spectrum, core design principles and the 1980s blueprint, designing your own microcomputer, building a modern portable Spectrum, moving from prototype to a printed case, selecting your development tools, conclusion, and further resources. I will use the gathered sources to support the content. phrase that launched countless retro-computing dreams, "The ZX Spectrum ULA: How to Design a Microcomputer," is more than just a book title—it's a design philosophy. At its heart lies the Ferranti ULA (Uncommitted Logic Array), a clever chip that engineered a computer revolution. This guide draws from the masterclass provided by the book and the vibrant community it inspired, exploring the secrets of the original ULA and charting the path to building your own portable microcomputer. In a modern design, you can eliminate this
If you are building a ZX Spectrum portable (often called a "ZX-clone" or handheld), you have two paths:
Understanding the ULA has allowed the global retrocomputing community to keep the ZX Spectrum alive indefinitely. Projects like the have taken the reverse-engineered ULA logic and expanded upon it, adding enhanced graphics modes, faster CPU speeds, and SD card support—all while maintaining 100% backward compatibility with the original 1982 software.
It takes a 14 MHz master crystal oscillator and divides it down to provide a 3.5 MHz clock to the Zilog Z80A CPU. adding enhanced graphics modes
Integrate a highly efficient buck-boost DC-DC converter to provide stable 5V and 3.3V rails required by your processing units and display.
No portable is complete without a case. Use or Fusion 360 .