Kempston Joystick Interface

Kempston compatible joystick Interface for ZX Spectrum computers. It has full 8 bit address decoding and uses just two chips: 74HC688 and 74HC540.

 

It has full 8 bit address decoding (minimizes clashes with other devices), supports up to three fire buttons and has a short circuit protected +5V supply suitable for auto-fire joysticks. All this using just two chips: 74HC688 and 74HC540.

 

Notes: R1 (47 ohms) should be a metal film resistor rated at 600mW.

Done