Steady Hand EEPROM Programmer
8 points by dzwdz
8 points by dzwdz
It's a discrete-logic hex editor! I'm an electronics noob, but the circuit looks relatively simple - and, all things considered, it looks pretty usable too.
I'm submitting this here because bootstrapping efforts seem on-topic. I'm not really sure what's the next step here - I wonder if there are some e.g. RISC-V boards that can boot directly from an EEPROM.
it could be even simpler: all you really need are a bunch of DIP switches connected to address and data pins, as well as some push buttons on a very small number of control lines. but that gets tedious extremely fast (and is pretty error prone).
most of the circuitry in here is for affordances against the tedium. and i think one can safely skip all the timing related circuitry (the at28cXXX series doesn't have any maximum timings for any part of the programming procedure).
i was a bit surprised to find that there really isn't a jelly bean hexadecimal to 7segment decoder in the 7400 or 4000 series (kinda understandable, given the prevalence of octal back then, but still). so unless you want to buy some obsolete motorola, natsemi or fairchild chips off ebay, the diode matrix actually seems the easiest way for that.
This is incredibly cool.