søndag den 12. april 2015

Z8671: Tinybasic on a z8 processor

When burrowing though a big box of unsorted IC's, like Scrooge McDuck though his money bin, i came across a chip I'd never seen or heard of before: Zilog Z8671 (BASIC/DBUG). Upon reading the "Zilog Z8-something" part i got hyped because i assumed it was a Z80 support chip, like the standard 6800 support chips are all called 6850, 6821, etc. and 8080 chips are called 8212 and so on.

I was very very wrong, but that didn't diminish the hype. The Z8671 is a chip in Zilog's Z8 microcontroller series: one that has an internal mask ROM with tinybasic! 

Later I found some information leading to a Steve Ciarcia's Circuit Cellar (a series in BYTE magazine) that spoke about this tiny MicroMint z8671 board (Micromint is still around, it seems). -Alas it was much later that i found an actual schematic for the system, and was able to start the work.

A similar circuit is shown in the Z8 handbook/application book, but it had certain oddities: it was meant for the z8671, but it still incorporated a 27128 EPROM, with no explanation as to what was to be put in it. (Also, at that time, i didn't have access to an EPROM-programmer, which i do now, and now consider the greatest and most vital tool in DIY computer electronics at all: EPROM PROGRAMMER: backup-ing vintage ROM's, writing your own rom's for systems; even setting EPROMs up as programmable logic!

Anyway, decided I wanted to do the machine with wirewrap: had all the ic sockets and a nice eurocard protoboard to build it on.
-Had little to no wirewrap wire, though. It arrives tomorrow, updates will follow, but so far:

The Toshiba RAM is a placeholder IC, since I used two loose SIP wrap lists and needed to hold them in place: the same with the Z80 processor: I keep a box of dead or useless IC's for this kind of purpose, also to mock-up component layouts.

My only problem is: I have only one of these IC's. So if the z8671 I have turns out to be a goner, I'm screwed.

That's it