kernelthread has recently become one of my favorite contributors.
That's what I was waiting to see ... a multi-purpose design. Now I'm more interested.

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Got a kilobyte lying fallow in your 65xx's memory map? Sprinkle some VTL02C on it and see how it grows on you!

Mike B. (about me) (learning how to github)

I thought that was always part of the concept, tbh.

_________________
Want to design a PCB for your project? I strongly recommend KiCad. Its free, its multiplatform, and its easy to learn!
Also, I maintain KiCad libraries of Retro Computing and Arduino components you might find useful.

Yes; in fact I would put that more strongly. The extra learning curve that comes with an Arduno or Pi may be not only unsatisfying but actually daunting. Yes there are some useful skills to be acquired, as Michael says, but making those skills an actual requirement is worrisome, IMO. We need to be cautious about how many prerequisites get placed in the beginner's path.

A segue: one skill many novices will need to refine is soldering. And it's alright if the proposed programmer kit requires soldering, because the 65xx project itself will very likely require soldering, too. But the bar will be set uncomfortably high if the novice is required to solder an FT245R with its 0.65mm lead pitch! (Or is it the plan to use one of the FT245R modules that're available? No tricky soldering, but it's a lot more expensive than the chip itself.)

I may be guilty of some favoritism but my discrete asynch approach (100% through-hole) is easy to solder... and, FWIW, it could also include some of the extra functionality that's been mentioned, such as supplying a clock, or taking control of RDY.

Segue again: I have mixed feelings about the extra functionality, regardless of whether it involves FT245R or an enhancement to my Dumb Asynch. Naturally the added features seem attractive to me, but I have enough experience to comfortably take them in stride and put them to use.

But where a novice is concerned there may be something to be said for a KISS approach. IOW, let the EPROM programmer simply be an EPROM programmer. Then blasting the chip becomes one goal, and when that's achieved we have no further need to interact with the programmer. Instead, we take the programmed chip and interact exclusively with the project.

Don't get me wrong, I love tricks like this that use cleverness to achieve disproportionate goals! But I'm not sure we should be putting them on the menu for a newb.

-- Jeff

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In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

Makes me wonder...

Is there such a thing as a 6502 newb that isn't already WELL versed in the arts?
For sure in 1980 there would have been such a newb as the 6502 was a viable and affordable place to start the journey.
But today the 6502 is a trip down memory lane, most likely for those like myself that are just tired of today's bloated and disposable tech.

I wonder if there is a single person here thinking of connecting a 6502 that doesn't already have a few duino/pi boards sitting around or at least a few decent breadboard projects that include some kind of micro?

Brad

Okay, I hope it doesn't seem like I'm arguing, because you raise a valid question. But I would rephrase the question and ask, what proportion of 6502 enthusiasts haven't yet acquired these Arduino and Pi skills? I'm sure there are some, and perhaps quite a few. (In fact I'm in that camp myself! Just never got around to it, and so far have been quite content without.)

-- Jeff

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In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

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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?

Interestingly I have not worked with Arduino nor Pi. In late 1990's I designed and programmed with AVR AT90S2313 for few small applications and last 5 years of my career I designed with synthesizable ARM7TDMI in verilog source, but these are detailed hardware designs and bare metal programming, nothing like the high-level abstraction in Arduino and Pi. Frankly I find manipulating high level objects and library routines unsatisfying. My feeling is 6502 newcomers also want to see behind the curtain how things really work.
Bill

I've not made a project with a Pi either, but I have used a Pi 4 as a cheap small form factor Linux system. It is currently connected to my living room TV, with a USB wireless mouse and keyboard. Aside from casual web browsing and video watching, I use it whenever I need Linux - or when my wife needs to use my desktop, usually to do some printing.

If I disconnected it and took it out of its case so I had access to the GPIO pins I suppose I could do a project of some sort with one.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

Getting back to the original post... I had assumed you were talking about programming single voltage EEPROMs, like the 28C256, rather than actual multi-voltage EPROMS. Is that a correct assumption?

This is not meant to be a general purpose programmer, so it will target one common, cheap, available EPROM like SST39SF010, about $1.50 from Mouser. It is a single voltage programmable device.


Jeff,
When I said "FT245", I do mean an assembled module like this. It is $11.5, shipping included. I found mine that I bought 2-3 years ago, it looks exactly the same. Don't get me wrong, soldering is a critical skill that opens the door for experimenting with wide range of electronic components, but it needs practices and for visually impaired like myself, expensive capital investment in stereo inspection microscope.

I also like your serial bootstrap concept a lot. I've used serial port in CPLD to bootstrap either with a small bootstrap ROM or driving a DMA engine to fill RAM, but I've never fed opcode directly to a CPU. I want to emulate it in CPLD first before realize it with pc board.

It looks close enough to finalize the design into rev0 pc board. There are only EPROM/RAM/6502/oscillator and 2 TTL logic so it will certainly fit 100mmX100mm. Heck, it will fit 50mmX100mm so two pc boards per 100mmX100mm panel and weight lesser than 1oz to cut down the shipping cost. Rev0 will be 100mmX100mm to have prototype area for experimentation (like the serial bootstrap engine). I have couple other designs I want to send out to JLCPCB this weekend so timing is good.
Bill

On the FT245, there are two pins (labelled CBUS5 and CBUS6) which have a variety of functions. The clock you mentioned earlier is one of them. They can also be set to 0, 1 or Tristate. Their function is controlled by the FT245's internal EEPROM, which can be reprogrammed using the FT_PROG utility, or by using the D2XX API. The latter in particular would mean that you could write a program on the host PC which accesses the FT245 directly using the D2XX driver, and can thus toggle those CBUS outputs.

As an example, CBUS5 could be normally Tristate, but pulled low when we want to hold the 6502 in reset. CBUS6 could control the memory map of the 6502 SBC. Since both of these settings are held in EEPROM, once we've finished programming our SBC we can leave the CBUS outputs in the correct states for "normal" usage.

The downside is that we can no longer treat the FT245 as if it were a simple serial port: we would need to write a specialist application to program the SBC. That being said, I've reviewed the documentation, and it doesn't look that bad, and a dedicated programming application could make it even simpler for a newbie to get started, as the application itself could walk them through the process / automate as much as possible.

_________________
Want to design a PCB for your project? I strongly recommend KiCad. Its free, its multiplatform, and its easy to learn!
Also, I maintain KiCad libraries of Retro Computing and Arduino components you might find useful.

Okay, I see the objection to using the Arduino is coming mostly from folks that have never used an Arduino. There are no skills to acquire that anyone with a computer has not already acquired. If you can run a simple software install and know how to point and click you can program an Arduino with a pre-existing 'sketch' (the word Arduinoids use for program). It is literally that easy.

You don't have to learn C, you don't have to learn Atmel architecture, you don't have to learn any specifics about the MCU used in the Arduino. Here is the process:

1 - install Arduino IDE
2 - connect Arduino to computer via USB cable
3 - start the IDE
4 - open the 'sketch'
5 - click on upload
6 - in a few seconds you're all done.

There is a reason the Arduino is so popular. At the risk on being vulgar, near idiots can use it without issue as long as they don't have to develop anything. Heck, even I can use it!

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Bill

All true, re the Arduino... easy to get up and running with minimal to no fuss. I had a few of them some years ago, but really didn't find them that interesting. I didn't really like their tool set and schematic drawing, etc., so I eventually gave them away... still, they have their following and one can do a fair amount of things with them.

I still think there is some merit on the initial intent of this thread... to create a programmer using the 6502. I would likely envision an all-in-one board, where you can download code on a cold start, program the EEPROM/Flash, then actually run the code on the same system. Not sure if that is truly possible without some interesting design and possibly a CPLD, but I think this could be a neat project for newbies and folks who have already built a 6502 system.

Just my $0.02....

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Regards, KM
https://github.com/floobydust