Panasonic HHC ROM 'capules'

[Jeff_Birt]

I will know more about the ROM access time in a few days when I get a chance to look at it. What occurs to me though is that Panasonic instituted the /8 of PHI0 for this reason. The OS has to set that register in the Y-Driver chip. Then proceed to do what else it needs to do before trying to actually read from the ROM. It seems Panasonic must have had this in mind too, but the proof will be in the pudding, or testing in this case. The 'short circuit' of the ROM power still bugs me too, given that most of them have a 0.1uf cap strapped across the power rails it seems a terrible waste of power.

I used Fusion 360 to create the model. I printed a sample last night which came out pretty good. It fit even though the filament used is not ideal. There are a few minor tweaks left, then I'll try a PCB carrier. I also need to try and rig up a way to plug this style carrier into a Molex 78802 socket. This is the typed used on the TRS-80 Model 100 and I have spares. This will allow building an adapter PCB to program the EPROMs in situ on the carrier.

   

[EdS2]

Would a suitable circuit with a capacitor and a diode allow the flash to remain powered in between relatively frequent accesses? Then a delay would only be needed for the first access after some time of inactivity.

[brouhaha]

(01-25-2023 03:23 PM)EdS2 Wrote:  Would a suitable circuit with a capacitor and a diode allow the flash to remain powered in between relatively frequent accesses? Then a delay would only be needed for the first access after some time of inactivity.

I've considered that. At first I didn't think it would be workable because there's no chip select available. However, because the HHC actively pulls the power back down, one might be able to add a CMOS inverter (powered by the diode and capacitor), and drive the flash chip select from that.

The tradeoff is using a high enough capacitance to make it work reliably, but low enough that it doesn't require so much initial charging current to cause a problem for the HHC electronics.

[Jeff_Birt]

I have designed a PCB carrier that looks like it will work. The trick now is to be able to get it back out of the socket. Having a handle in the middle of the PCB like the chip carrier does would not be ideal. Luckily the handle of the chip carrier sticks up 2mm above the top of the socket, so we have a bit of extra room.

I came up with three ideas below. I'll print out all three and mill out a dummy PCB to test how easy it is to install/remove.

A) Pair of holes in each end requiring fabricating a tool from a paper clip to pull the carrier/PCB out.
B) Raised section each end with rectangular hole
C) Raised section each end with rectangular nub

   

   

   

[brouhaha]

Those look great!

When I was thinking about this many years ago, I had this wacky idea that I'd put the PCB with the SMD component side down, and have the carrier have a solid "sheet" of plastic above that, and with the handle in the middle like the original. I'm not sure whether than really can be made to fit. Of course, it requires that there not be any tall components.

Thinking more about it, this wouldn't necessarily even require that the PCB be mounted upside-down, though that's probably easier in terms of having a simple means to attach it to the carrier.

[MattPilz]

Hi all!

I was really surprised to stumble into this thread and the impressive amount of work members have done in researching this system. I had gotten into the HHC a few years ago but never found much of any info online about it. I'd started plans for an information website on it and began documenting all the ICs, memory map and so on but never finished the idea, yet.

This year I used my HHC full briefcase set to connect to a BBS via a landline and its acoustic modem and last year dabbled into developing software that interfaced with its rare video display (which uses the same chip as an MC-10 and original Tandy Color Computer).

I only have the Microsoft BASIC capsule but have always been interested in the SnapBASIC and SnapFORTH variants. MS BASIC does support POKE/PEEK but relies largely on control / escape characters to do very much with the system itself. Whereas the others were native to the system so you could much more easily interface with I/O devices. Really appreciate the link to the other forum that contained dumps of many capsules, as I had rigged up my own dumping system but had not anything unique to really dump. Now to figure out how to recreate new capsules with things like SnapBASIC and we'll be good to go! Love the 3D model and work on that front too, to create some form of modern EPROM-compatible capsule carrier.

I can't thank Paul Berger enough for sharing those technical documents, I had not seen either of them previously and they are a wealth of information! At one point I had gotten in touch with one of the original engineers of Friends Amis who created a lot of the documentation and software concepts for HHC and he had donated his HHC materials to a museum (which sadly doesn't have any of it digitized). He seemed willing to chat so some day I hope to find time to follow-up or perhaps arrange for the guys at Floppy Days to do an interview with him, since it is all fascinating history to me.

Here's my briefcase HHC online this year:



And here was when I first was interfacing with the display adapter to get colored semi-graphics:



QUESTION: Does anyone have the manual for SnapBASIC? That seems to be lost in time. The SnapFORTH, SnapBASIC and HHC Book have been digitized on archive.org.

[KeithB]

A thought: An MSP430 could be powered forever from a coin cell and just respond rather than turning itself on and off. The only issue would be the level shifting.

[jr2xzy]

Hi, all of this thread.

It is successful to make a 32KB ROM capsule which contains 2 of 16KB capsule images and one of two can be selected.
It took several years to find a proper NMOS EPROM for Panasonic HHC.
If you interested in this capsule, please look through my web site
https://jr2xzy.blogspot.com/
in the title of "Panasonic HHC - Reproduction of 16KB program capsule" by using Google Translator.
You may be able to make the capsule, if you have a suitable experience to make it.