tirsdag den 9. juni 2015


So yeah. Am doing modular synthesizers now. Still will do computers once in a while, but NOT NOW!

Here's my synth so far. All modules homemade. To the eurorack std.

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

torsdag den 1. januar 2015

Progress! Lack of progress! TESTGEAR!

So It's been a while. Been doing some RF projects for ham radio the last months, and been a bit out of the loop with the microcomputers. Until my interest was sparked by a piece of test gear:

I got a logic analyzer! Thurlby (Tti) LA4800 48CH. logic analyzer!
It was fairly cheap, even though it lacks the probes. The thurlby analyzers uses these pods with IDC connectors, which basically just contains some input protection and some buffers. It says in the manual that you really just COULD connect wires directly to the input connectors, but there is NO input protection what so ever. they feed right into some standard 7400-logic buffers and some SIP resistors for pullup(down?), so if you feed it a smidgen more than 5V, you burn those (at best). Probes are coming along nicely, probably done by tomorrow (might make an update on them). 

The interface is really nice, it's intuitive, took me ½ an hour without manual to get a basic understanding of it. It does both timing and state analysis, and also has an external clock input.

It comes with some nice sets of default settings; 8 bit computer
being one of the better. Pictured is some banks of test data it had.

The hardware seems dated 1992- design is probably late 80's early 90's. 

The main board is almost entirely trough-hole, the only smd stuff being the LCD drivers on the module. 

Most chips are 7400-series, with some nice big RAM for the datalogging. processor(s), yes, it has two, each associated with an eprom and some more ram; I'm suspecting one set is purely for the RS432 communications. Anyway, processors are Hitachi HD6303 processor.

The display has wonderful contrast, even contrast and brightness setting. 

Truly a very neat bit of gear.