[pbourke]

> but the kit supplier itself can't migrate from Hitachi MCU because they don't have firmware sources as they themselves only copypasted the firmware as a binary for decades..

That’s seems like a rather existential problem. If I’m understanding correctly, the kit supplier makes the control board and the manufacturer does final assembly?

[baybal2]

Yes, and the Chinese kit supplier seemingly got the tech from a Japanese aircon maker somewhere in nineties, and then copied the board verbatim ever since.

[pbourke]

I wonder if you could run the firmware in emulation on a more recent CPU.

[baybal2]

I don't think one can even fund assembler docs for a chip so old, rare, and obscure as first SH-1,2,3 families.

[AlotOfReading]

This is a weird comment. One of the key features of the SuperH ISA is that it's more or less backwards compatible. I worked on them in the 00s/10s, but I can't imagine they had an entirely different ISA in the 90s. I also know that commercial SH3 emulators exist because I've used them. Heck, Renesas used to ship one with the toolchain.

[baybal2]

I'm surprised to hear this, maybe trying to salvage the old binary might have had some sense, but the client already went for a complete re-engineering, recognising the low availability of this rare chip as a great threat.

[AlotOfReading]

Yeah, they definitely got rare in the normal supply chain. I'd be surprised to see one in anything other than a japanese design today.

[pbourke]

I don’t know anything about these, but found it interesting that people have ported Linux to these chips as they’ve come off patent:

https://en.m.wikipedia.org/wiki/SuperH#J_Core

[baybal2]

That is for much more recent, and bigger cores.

The one I talk about has a kilobyte of ROM, and is an original SuperH from early nineties.