Panasonic HHC ROM 'capules'

[brouhaha]

(01-03-2023 05:19 PM)Jeff_Birt Wrote:  you can't create SnapFORTH programs without the SnapFORTH 'ROM capsule'. (But you can run them without it.)

The SnapFORTH development ROM was 16KiB and wouldn't fit in a capsule. It was an expansion box, about the same size as e.g. the RS-232 expansion box, but without an I/O connector. Inside there are EPROMs and logic for bank-switching.

Technically a capsule port could address 16KiB, but the capsules are 24-pin, and there was no 16KiB 24-pin EPROM. Even the 8KiB 24-pin EPROMs were and are relatively uncommon; normal 8KiB EPROMs (Intel 2764 and equivalent) are 28-pin. The only 24-pin 8KiB EPROMs were the Motorola MC68764 and MC68766.

If one somehow made a 16KiB capsule, I'm not sure whether SnapFORTH would run from it, or whether it requires some of the logic in the expansion box.

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Has anyone created images of any of these capsules. I have had no luck finding them on the web.
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There are images around. I have some but I'd have to do some digging to find them.

One thing to be aware of is that the commonly available images of the Microsoft BASIC capsule have a corrupted byte. I posted about that on cctalk some years back with details on which byte, and what the likely effects were:

https://marc.info/?l=classiccmp&m=120657197412183&w=2

I spent some time reverse-engineering the HHC "intrinsic" (internal) ROM and some of the plug-in ROMs. I put the work I'd done on the intrinsic ROM and the SnapFORTH ROM on github:

https://github.com/brouhaha/hhc

Quote:One really odd thing about the Panasonic HHC is that it uses an NMOS 6502 processor (Rockwell), in a 40-pin DIP. It looks like there were trying to come up with something quickly using COTS parts.

It may seem odd, but it was the only practical solution when the HHC was developed. The HHC was introduced in fall 1980 in Japan (early 1981 worldwide), and development was started in 1978. There was no suitable CMOS microprocessor at the time it was developed; the 65C02 wasn't introduced until 1983. The only commercially available single-chip CMOS microprocessors in existence in 1978 were the Intersil IM6100 (PDP-8 12-bit instruction set) and RCA "COSMAC" CDP1802, both of which were much slower than the NMOS 6502.