The Zx Spectrum Ula [cracked]

The primary "solid paper" (and definitive technical reference) regarding the Sinclair ZX Spectrum's custom chip is the book by Chris Smith.

The "Uncommitted" part of ULA is key. Ferranti would manufacture a silicon die containing a fixed array of unconnected NAND gates, inverters, and flip-flops. The final "commitment" was a single metal layer that connected these components into a specific circuit designed by Sinclair. the zx spectrum ula

If you are looking for academic-style papers or guides beyond Smith's book, you may find the following useful: a ULA emulator must model:

To save memory, the Spectrum uses a unique color scheme: the zx spectrum ula

The ULA is the single hardest component to emulate accurately. While a Z80 emulator is straightforward, a ULA emulator must model: