Some while ago...
I designed a bicycle "computer" , actually just a poor speedo and odometer, with only a z80 and an eprom (and a 4 Digit display.
To keep the battery consumption below a megawatt , the z80 halt was asserted (and probably the clock stopped as well) after it had calculated the speed and incremented the wheel rotation count. It was woken by a reed switch and magnet on the wheel each turn or by a button to read the display.
There are enough static registers in the z80 not to require external ram and enough address lines to multiplex the display without any (or minimum) decoding.
I designed a bicycle "computer" , actually just a poor speedo and odometer, with only a z80 and an eprom (and a 4 Digit display.
To keep the battery consumption below a megawatt , the z80 halt was asserted (and probably the clock stopped as well) after it had calculated the speed and incremented the wheel rotation count. It was woken by a reed switch and magnet on the wheel each turn or by a button to read the display.
There are enough static registers in the z80 not to require external ram and enough address lines to multiplex the display without any (or minimum) decoding.
Statistics: Posted by BillTodd — Fri Jan 16, 2026 9:31 pm