The amazing 6502 support chip: The 6532 RIOT!
https://youtu.be/Fo5bwoBWVhU

I hope I didn’t get too many things wrong

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New new new new new video out! Serial Bootloader for my 65uino
Also, check out: I2C on a 6502 Single Board Computer
and Complete hardware overview of my 6502 SBC R1

I thought it was a nice video, Anders.

I've always been fascinated by some of the early small systems that included a 6532, like the 82-300 board from John Bell Engineering, the Beta, the CEPAC-6502, and the EMUF 6504. Several of which have been described on Hans Otten's site.

Cheerful regards, Mike, K8LH

BTW, I have a few of the 2-MHz G65SC32P-2 CMOS version which were manufactured by CMD or GTE. They seem to be getting harder to find at a decent price.

Thank you

Yes! Exactly! Deep down I know I’ll end up with something comparable to a 50 cent modern MCU but it really is tempting to make a minimal 6502 system like this - and then go overboard with blinkenlights and toggle switches on a real front panel

With the 65c02 it might even be possible to skip the ROM and toggle 128 bytes of code straight to RAM… NMOS would require extra separation/buffering

_________________
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New new new new new video out! Serial Bootloader for my 65uino
Also, check out: I2C on a 6502 Single Board Computer
and Complete hardware overview of my 6502 SBC R1

Looking at the John Bell schematic, I am shocked a 2N2222 is fast enough to act as an address decoder. I tried to use one as an inverter with my SBC and it couldn't switch fast enough. So I ended up using an inverter IC and having a bunch of unused logic gates.

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Would you mind posting a diagram of that Garth? Sounds interesting!

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Thanks!

I'm trying to work out why that stabilises with OUT at around a quarter of a volt, with e.g. a 5V supply and IN=4.5V. The diode pulls OUT up to e.g. IN-0.3V, minus whatever is dropped across the resistor - so I guess the base current through the transistor means enough voltage is dropped across the resistor to get OUT down to a low logic level? Is there a better way to think about this, my mental model doesn't feel very good!

Edit - ah I think I get it, the transistor's base will be about 0.6V-0.7V above its emitter, the drop across the resistor covers the rest, drawing whatever current is required for that, and the diode only pulls OUT up to about 0.3V less than that VBE voltage.

The Schottky diode diverts excess base current (that would've saturated the 2N2222) to collector. This is sometimes called the "Baker clamp" although the original Baker clamp was 2-diode circuit.
Bill

I did not as I didn't know it would help. Seeing your links was interesting.

15k and 20pF makes that an RC clock of 530516 Hz .. right?

_________________
---
New new new new new video out! Serial Bootloader for my 65uino
Also, check out: I2C on a 6502 Single Board Computer
and Complete hardware overview of my 6502 SBC R1

Another question about the transistor 'decoder' on that John Bell 82-300 board, if I may?

Knowing enough about electronics to be dangerous... would an N-channel MOSFET (2N7000 perhaps) be a suitable replacment for the 2N2222 BJT? I noticed San Bergmans used something like that on his 6802 Nano board. Any potential issues trying this on a copy of the John Bell 82-300 board with a 1-MHz clock?

TIA. Mike, K8LH

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?