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Another Vintage Z80 palmtop compy

A project log for Vintage Z80 palmtop compy hackery

It even has a keyboard!

esot.ericesot.eric 06/13/2021 at 23:490 Comments

Found a TI-83 Plus at Goodwill, just now... I don't really plan to "switch teams," at this point, though I haven't really gotten too fond of the 86's menu system despite ogling the 85's in my 82 days... I find it more flashy than functional. But, I'm pretty familiar, now, with the 86's innards and potential for hackery, and yah know that's my jam.

...Though, the 83+ has FLASH... Hrm...

Anyhow...

The main idea, at this point, is another point of reference for the linking issues in the last logs. May be similarly useful in other ways.

It's been on the shelf there for well over a month, I guess they're no longer in as much use in schools around here these days. So, I don't feel like I'm keeping it out of the hands of a kiddo who needs a deal. And, it may also mean that these things, abundant as they once were, will become available in large quantities to "hackers" like me to do interesting things with... I dig finding uses for what others deem no longer useful... Keeping them outta the landfills....

Z80's being still in use in products even these days, it's still got decent potential for low level Z80 learning...

And from what I've gathered it should be possible to throw a tiny bit of logic at the memory-bus to make for memory-mapped I/O, even throw a UART at it...

So, now the thing could be used like a bulky microcontroller of sorts. Which just happens to have a screen and keyboard... I dunno, I kinda visualize it atop a robot kinda like HERO, as the brains... Who knows. Maybe a bit ridiculous these days, but... Seemingly doable, anyhow.

I also envisioned a bunch of teeny toggle-switches (No, DIP switches do NOT sound fun to toggle!) and LEDs at the space at the bottom of the keyboard, get some hard-core coding goin' on, kinda like this guy:

...

This makes working with the 83+ seem a lot more appealing :/

https://www.ocf.berkeley.edu/~pad/faq/ti83.html#5

Lots of discussion regarding "FLASH applications" and "archive memory" which both sound like they're stored in flash memory.... which, again, would be quite nice to use while trying to code /on/ the device... seeing as how my last assembly program attempt wiped the RAM of the 86, because I forgot to add "ret" at the end.... whoops.

OTOH, the challenge of adding FLASH to the 86 is one that has its appeal. Physically/electrically it looks to be relatively simple enough... a few bodge wires, maybe, for an extra address bit. Or maybe a tiny bit of logic. But, software-wise, we're talking a bit of a challenge, since where would we store the actual code to actually access what's in the extra memory-space that's not accessible by the ROM-based OS, but in a RAM-based application which could get wiped...!

Thoughts are: there seems to be one ROM page which is empty... so maybe the boot-rom could be modified/appended slightly... (but, accessing /that/? Maybe only via a tiny hand-entered "hex" application? Which could almost as simply just go straight to one of the /other/ addresses in FLASH not originally dedicated to the OS... and, then, the flash chip could actually be mostly piggy-backed on the ROM, so wouldn't have to copy its contents and desolder...) but, still, that means the only way to access it, after a wipe, is with a special program which would have to be copied-over either from a computer or hand-entered... anyhow, and then, of course, applications to move things around between executable memory-ranges, etc... Not a small endeavor, but doable I think. 

Also, those notes regarding the 83+ make it sound like maybe TI might've gone out of its way to deny access to certain/extra memory addresses... which could put a huge damper on adding mem-mapped I/O. So, still not switching teams...

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