32 Byte Diode PROM

A project log for Hardware Controlled 4 bit CPU

A hardware controlled 4 bit CPU based on lessons learnt from the TD4 and the CHUMP CPUs

agpcooperagp.cooper 12/15/2022 at 01:500 Comments

32 Byte Diode PROM

I felt that a 16 byte diode PROM was too small. You cannot fit a program with a subroutine in 16 bytes. So I designed a 32 byte diode PROM, but unfortunately I could not get the auto-router to work. SO the answer is two 16 byte daughter boards:

Here is the schematic:

One nice thing is that the boards are stackable.

I will have to put back the page circuity on the mother board.


I have sent the PCB off for fabrication. Usually takes 5 or 6 days.


I have made a mistake with regard to stacking the boards. You cannot get 20 pin long headers, typically they are 10 pin headers, and you need a gap between them. Oh well!

I designed a PCB for the 10 long pin headers:

But I am not getting them made until I use up the previous design.