CD-ROM board: HD64F3039 = H8/3039 = H8/300H

A project log for Repurposing OTP/mask-ROM microcontrollers

Many microcontrollers with internal ROM can be configured to run from external ROM!

Eric HertzEric Hertz 12/04/2022 at 12:360 Comments

I'm Reorganizing, bare with me...


I was planning on starting this "project" with a more 'vintage' uC (e.g. the 6502-compatible I found at the bottom of the box) but this is the order of the pictures on my phone, and reorganizing with a thumb is a PITA, so I guess I'll start with this one. 

And, actually, maybe it's a good thing, 'cause it shows this "technique" is still useful with more current eWaste, as well...

This was the interface board from a CD-ROM drive, as I recall. Most of the time, I've found that their chipsets are very closed secrets. But this one has a good ol' microcontroller.

This is a Hitachi (now Renasis) H8/3039 which is apparently a 16/32bit microcontroller. 

The F in 64F3039 indicates that it's in-system-programmable, BUT: who has the time/energy to figure out that protocol, when you can just attach an E[E]PROM?

Actually, more-importantly, [yeah, I'm going about this documentation all backwards] is the underlying concept, here, that seems applicable to the wide number of assorted uCs one might encounter in old junk.

Anyhow, Wire-up the "mode" pins to Mode1 or Mode3, add a regular ol' external EEPROM, and whatever the heck is in the flash is completely irrelevant.

It'd make a heck of a lot more sense if I'd started with the 6502, 8031, and similar "fallback-mode" devices, instead. But I need to get this list documented for my own purposes...