It managed the priority between the Z80 CPU and video display needs, often pausing the CPU to avoid screen flickering. System Timing: It generated the 3.5 MHz clock for the CPU.
0;e8a;0;2cb; 0;908;0;f1; 0;88;0;98; 0;279;0;17a; 0;1234;0;b19; It managed the priority between the Z80 CPU
Inside the Heart of a Legend: The ZX Spectrum ULA If you’ve ever wondered how Sir Clive Sinclair managed to squeeze a full-blown color computer into a tiny plastic wedge for under £100, the answer lies in one piece of silicon: the Uncommitted Logic Array (ULA) In the case of the ZX Spectrum, the
The 324-page volume is structured to take a reader from basic semiconductor theory to full system implementation: www.librador.com The ZX Spectrum Ula: How to Design a Microcomputer - Amazon including: For the Spectrum
A ULA is a type of integrated circuit (IC) that contains a large number of logic gates, which can be interconnected to perform complex digital functions. In the case of the ZX Spectrum, the ULA (also known as the "ZX Spectrum ULA chip" or " Ferranti FDC 1016") is a custom-designed IC that integrates many of the computer's core functions, including:
For the Spectrum, Sinclair’s mandate was absolute: The traditional solution (a dedicated Video Display Controller like the Motorola 6845) was too expensive and required external character generators and RAM. The ZX Spectrum ULA was the answer: a custom gate array designed by Richard Altwasser of Ferranti, programmed to do just enough and nothing more .
Further reading: Chris Smith’s "The ZX Spectrum ULA: How to Design a Microcomputer" (an actual book) – This article is the executive summary; his book is the masterclass.