Close
0%
0%

Timer Retrofit For Z80 SBCs

Quite a few simple Z80 SBC systems don't have a timer interrupt or clock of any kind. CP/M 2.2 after all didn't need one.

etchedpixelsEtchedPixels
Following
Liked Like project

Just one more thing

To make the experience fit your profile, pick a username and tell us what interests you.

Pick an awesome username
hackaday.io/
Your profile's URL: hackaday.io/username. Max 25 alphanumeric characters.
Pick a few interests
Projects that share your interests
People that share your interests

We found and based on your interests.

Choose more interests.

OK, I'm done! Skip
Similar projects worth following
144 views
1 comments
1 followers
View Gallery
The board itself is a simple clock generator using a 74HC4060 14 stage ripple counter. 2.45MHz goes in one end, 150Hz comes out the bottom. Along the way it generates a bunch of useful other clocks for serial ports.
Because almost all the SBC systems without timers seem to use Z80SIO or 16x50A UARTs there is no bus and interrupt line logic. Instead the 150Hz from the board can be fed into one of the modem control inputs and the UART itself provides both interrupt masking and control.

timertick.kicad_pcb

x-kicad-pcb - 68.81 kB - 11/09/2019 at 14:00

Download

timertick.sch

x-kicad-schematic - 4.82 kB - 11/09/2019 at 14:00

Download

  • 1 × 74HCT4060 Logic ICs / Counters
  • 1 × 0.1µF capacitor
  • 1 × 8pin can oscillator to suit your needs
  • 1 × Misc Headers
  • 1 × Double sided sticky tab to stick onto sbc

Enjoy this project?

Share

Discussions

freefuel wrote 07/04/2023 at 00:59 • point

Now that I've found this I'm reminded of a watchdog timer I have been thinking of, it was something along the lines of 2 to 4 32-bit programable counters running at 1x to some Nx divided down rate, when the timer trips it resets to it's programmed setting while outputting one of the z80 interrupts so it can be used in any of the three modes. 

  Are you sure? yes | no

Similar Projects

Z180 processor board
Project Owner Contributor

STEbus Z180 board

keithKeith

A multi-purpose I/O card using the 26C92 and intended to be the pair for the 68008 CPU card
Project Owner Contributor

SC26C92 Dual UART/Timer/GPIO for RC2014

etchedpixelsEtchedPixels

68B09E processor board renovation
Project Owner Contributor

STEbus 68B09E

keithKeith

Like the title says ...
Project Owner Contributor

Z80 SBC with TEENY 2.0++ System Controlelr

johnny-questJohnny Quest

Does this project spark your interest?

Become a member to follow this project and never miss any updates

Going up?

About Us Contact Hackaday.io Give Feedback Terms of Use Privacy Policy Hackaday API

© 2025 Hackaday

Yes, delete it Cancel

Report project as inappropriate

You are about to report the project "Timer Retrofit For Z80 SBCs", please tell us the reason.

Send message

Your application has been submitted.

Remove Member

Are you sure you want to remove yourself as a member for this project?

Project owner will be notified upon removal.