You want a deep feature — a portable retro microcomputer based on the ZX Spectrum ULA. Below is a structured, actionable design specification covering hardware, ULA emulation/replication, firmware, power, I/O, enclosure, and manufacturing considerations so you can build a faithful portable Spectrum-like machine.
The original ZX Spectrum ULA is a locked treasure chest. But by understanding its functions – video, contention, I/O, refresh – you unlock the blueprint for any Z80-based microcomputer. To build a modern portable, you don’t reverse-engineer the silicon; you re-implement the behavior in an FPGA.
Your action plan:
The ULA taught Sinclair how to design a microcomputer on a shoestring. Now, it will teach you how to build a retro computer portable that fits in your backpack. The ghosts of 1982 are waiting for your solder smoke.
Keywords integrated: the zx spectrum ula, how to design a microcomputer, zx design retro computer portable. You want a deep feature — a portable
Here’s a feature overview for a retro-inspired portable microcomputer based on the ZX Spectrum ULA design philosophy:
| Challenge | Solution | |-----------|----------| | Contended memory timing | FPGA generates WAIT signal to Z80 exactly per original ULA. | | LCD scaling | 256×192 to 320×240: use pixel doubling or scanline buffer in FPGA. | | Keyboard matrix | 8×5 matrix via ULA port 0xFE; scan with FPGA and map to modern tact switches. | | Audio | Simple 1-bit PWM (original beeper) filtered through RC to speaker. | | Loading software | SD card + FAT32 + .tap parser; FPGA feeds bytes to Z80 via “divide-by-256” trick (simulate tape input on EAR pin). | | Case & portability | 3D print case with 40-key membrane (can source from ZX81 keyboard replicas). | The ULA taught Sinclair how to design a
The ZX Spectrum, released in 1982 by Sinclair Research, defined home computing for a generation. At its heart lies the ULA (Uncommitted Logic Array), a custom chip that integrated video generation, memory arbitration, I/O, and system timing. This paper explores how to design a portable, battery-powered ZX Spectrum-compatible computer by understanding, emulating, or replacing the ULA with modern hardware. We examine the ULA’s original functions and present a practical architecture for a handheld retro device using FPGA or discrete microcontroller techniques.