How the ZX80 Works
6 hours ago
- #RetroComputing
- #ZX80
- #HardwareDesign
- The ZX80 is a low-cost home computer from 1980, designed without a dedicated video chip, using TTL chips and a Z80 CPU.
- It generates video by executing NOP instructions and intercepting memory reads to draw characters on screen, causing screen flicker during keypress processing.
- Memory includes 1K RAM (upgradable) and a 4K ROM (expandable to 8K), with mirroring used for video generation and memory expansion.
- The clock runs at 6.5MHz, with the Z80 at 3.25MHz, synchronizing with PAL/NTSC frame rates for video output.
- Input/output uses minimal decoding for keyboard and cassette ports, and the design allows building clones like the Minstrel series.