Brian, If I understand your comment, I don't think you need an IC to do rom selection. I think the DAR uses a rotary encoder. When I first saw the DAR, I wondered about that. I'm pretty sure I found the part at Digikey. Very good! Steve
On Sun, Feb 26, 2023 at 3:51 AM Brian White <[email protected]> wrote: > Gratuitous use of another chip just for 2 OR gates to implement a 4:2 > encoder. It's all less efficient and less practical than the dial-a-rom, in > that the dar holds 16 roms and doesn't need another ic, and the dar > programming connection is even simpler and more robust. > > But it just amused me to have a direct selector without manually binary > encoding dip switches because why not? And I didn't want it to require a > tool to use either like a screwdriver. And of course I always want an open > source option, and I'm not up to the task of coming up with an open source > rex-alike but using a Lattice part and the open source toolchain. > > It's unfortunate timing but I had already started this at least 3 years > ago but just never finished it. A non-working version has been sitting in > that github since 2019. A few weeks ago I finally dusted it off and > corrected my bonehead pinout error, dialled-in the programming connection > so it works well (the holes are slightly closer together than the pins, and > the pattern and amount of offset took some trial & error) and replaced dip > switches with the slide switch & or gates. I had no idea the dar was in the > works. Not that it would have stopped me, but I just mean to say this isn't > a reaction. > > It's no competition anyway because only a very few people ever build these > diy-only things. I want them to exist so the option is there, but almost no > one actually employs it. So this is not touching anyone's sales. Besides, > *16* roms. And of course really it's even sillier when rex exists which > doesn't even need a programmer or adapter to load it's, what, 30? slots? > But for other platforms 4 is plenty. There's only 2 roms total for the 600 > for example. Still leaves 2 free slots for hacking. > > I just added the browser-friendly render of the schematic to the readme so > you can see the bank-select. > > -- > bkw > > On Sat, Feb 25, 2023, 8:18 PM Mike Stein <[email protected]> wrote: > >> How do you select among the 4 images? >> >> On Sat, Feb 25, 2023 at 6:50 PM Brian K. White <[email protected]> >> wrote: >> >>> On 2/25/23 10:31, [email protected] wrote: >>> > Morning all, >>> > >>> > I just made this video live this AM. The DARs for the Model T >>> computers >>> > have sold out already but my friend is making more. >>> > >>> > In this video we take a look at the ‘Dial-A-ROM’ a spiffy new >>> multi-ROM >>> > for vintage portable computers. It was designed by the same guy who >>> did >>> > the Backpack drive. First, we’ll learn how to use the Dial-A-ROM with >>> > the ROM images that come preinstalled on it. Then we’ll see how to add >>> > our own ROM images if we so desire. >>> > >>> > *https://youtu.be/CejyLsI0HIw <https://youtu.be/CejyLsI0HIw> >>> > >>> > Jeff Birt (Hey Birt!)* >>> > >>> >>> And for the diy-er, I finally vetted these last week: >>> https://github.com/bkw777/Teeprom/blob/master/4ROM.md >>> >>> -- >>> bkw >>> >>>
