This interface is the most popular and the best way to
connect joystick to ZX Spectrum. The port used is 31 (#1F) and
usually only A5=0 decoding is done. The idle is 0 (#00) value in
The interace contains inverted 3-state buffer, as input pins are
shorted to GND by the joystick, while this sets bits in port.
There are many constructions, you can see some below.
Files for download
- kjschem.gif 11.7kB (2002-10-12 20:18)
- Schematics. How to build Kempston Joystick from 74LS240 and 74LS32 chips.
- Kempston Joystick for YABUS.
- Internal Kempston Joystick interface, mounted under Z80 CPU (or over).