It's time. I'm making a Toggle Switch 6502 Computer

[AndersNielsen]

I've been wanting a 6502 assembly trainer for a while. It's a somewhat silly endeavour, but I'm going to make a RAM-only 6502 computer.

It's going to have the options of either single cycling every instruction from toggle switches or toggling in bytes to RAM.

Lot's of toggle switches, lots of LED's - especially since I both want to see what the 6502 is addressing and what the toggle switches are currently addressing.

This could be done simpler with a 65C02's BE pin but I'd like to use this to test 6507's and other 6502s too, so it has to be NMOS compatible - hence the 245's and the Woz-style single cycle circuit.

Lighting up 5mm LED's with a combination of either 4k7 ohms or 2x 4k7 ohms might be a bit dim, but it'll also give an indication of what is driving the LED and 9k4 should still barely light up a red LED.

Am I nuts? Did I mess up anything completely? Will it work?

[GARTHWILSON]

One topic that comes to mind that I think will interest you is "Antares 6500 Concept," and another is "Happy New Year and happy hacking in 2016!"  Oh, and note that modern ultrabright LEDs don't need much current at all to be easily visible in normal room lighting.  I even used a red chip LED in a circuit at work as a voltage reference, running 100µA through it, and since it was not to be an indicator, it was ok to cover it with epoxy along with the rest of the postage-stamp-sized board for secrecy and to protect from moisture, and to my surprise, it shone through even the epoxy quite well!

[Yuri]

I'd put a 245 on the data switches, knowing myself I'd probably forget to put one in a floating state when I go to run the thing.

[drogon]

Nice to see other 6507 projects...

Mine:

https://unicorn.drogon.net/IMG_20231220_193620_DRO.jpg

Have you seen the Cactus project? It was discussed here a few years back...

http://www.commodorez.com/cactus.html

-Gordon

[barnacle]

An Altair 6502 does have a certain cachet to it

Neil

[AndersNielsen]

GARTHWILSON wrote:

One topic that comes to mind that I think will interest you is "Antares 6500 Concept," and another is "Happy New Year and happy hacking in 2016!"  Oh, and note that modern ultrabright LEDs don't need much current at all to be easily visible in normal room lighting.  I even used a red chip LED in a circuit at work as a voltage reference, running 100µA through it, and since it was not to be an indicator, it was ok to cover it with epoxy along with the rest of the postage-stamp-sized board for secrecy and to protect from moisture, and to my surprise, it shone through even the epoxy quite well!

These pages are a treasure trove - hard to come up with stuff that hasn’t been done
I think the 5mm ones generally take a bit more current - the smd’s I also run at 5V with a 15k resistor on my 65uino, but I guess I’ll have to test if I can get anything visible out of them at 9400 ohms.

Yuri wrote:

I'd put a 245 on the data switches, knowing myself I'd probably forget to put one in a floating state when I go to run the thing.

I expect the 4k7 resistors will make that less of a problem. Don’t think I can use that trick with the 6502 address bus.

drogon wrote:

Nice to see other 6507 projects...

Mine:

https://unicorn.drogon.net/IMG_20231220_193620_DRO.jpg

Have you seen the Cactus project? It was discussed here a few years back...

http://www.commodorez.com/cactus.html

-Gordon

So nice and compact!

Yes, the Cactus is nice, but it relies heavily on the ‘C02 features like BE and 0hz clock

This, oh so arbitrarily, has to be NMOS compatible

[BigEd]

Great idea for a project!

Worth mentioning:
Mini version of the OSI-300 trainer
Links within, of course.

[plasmo]

I had a front panel project for Z80 but found data entry via toggle switches rather tedious. I also didn't like the LED readouts, so I changed the data entry to PS2 keyboard and readout to 7-segment displays. This probably can be done with a microcontroller, but I opted for a CPLD approach. I think an universal front panel for retro processors are quite possible.
Bill

[BillO]

Nice idea!

[Martin_H]

Neat. I will have to deep dive into the schematic to understand it better. The Cosmac Elf works because the 1802 has a built-in DMA controller, so the CPU loads the toggle switch values into RAM. Here it looks like you're driving both the address and data lines and disconnecting them from the bus as well.

A video on YouTube YouTube channel is hopefully in the works.