Interfaces
- Main article: Kempston Interface
Kempston produced a number of joystick interfaces for the Sinclair ZX Spectrum to allow normal Atari-style DE-9 connector joysticks to be used with it. Apart from implementing existing joystick interfacing modes they produced their own standard which delivered the joystick state on the Z80 bus at port 31 (read in BASIC using IN 31). This meant that the joystick did not produce key-presses like the other standards and the method was soon borrowed by other interface manufacturers and became quite popular.
Read more about this topic: Kempston Micro Electronics