6502.org

Awesome! Great to see it working

Happy to hear about your success, rehsd. (Nice catch, Adrien!)

-- Jeff

I chuckled today. I went to connect a VIA to my 65816, and I pulled up the code I had originally written a few weeks ago for it. Guess what? It had the reset vector in it! So, somewhere along the way, I accidentally dropped the reset vector. Oops.

If you're interested, I have a VIA running now.

https://www.rehsdonline.com/post/65816-via1-working

https://youtu.be/kHPb11BXB1A

Your six(?) chip decode is clever because it has no wasted sections. However, you might have under-estimated the official latency by not counting the address latch. The result is still likely to require less than 100ns in good conditions and attain 4MHz with 150ns ROM. However, it is definitely possible to do more with less.

I'm alarmed by the size of your board which is almost four times the size of the smallest EuroCard - and that's above average on the 6502 Forum. Some of your problems might be caused by board area. In particular, you might have power distribution problems.
I quite like akohlbecker's "warts and all" approach due to its honesty. It is a very good compliment to numerous failures found within the 500 messages of POC Computer Version One. We learn more from the mistakes of others than their success. However, it is highly inadvisable to copy unresolved problems and I usually have to lurk on the The Plagiarist’s section of Reddit to find this level of unintentional comedy.

Actually, I've quite enjoyed your numerous messages on Reddit and I'm surprised about your second system effect.

100% behind you BDD. Being a math teacher, I know the power of failure: To learn what NOT to do, and try again. The hardest thing for any student of any topic is to try again. And again. And again if necessary. It is even hard for me. If pointing out problems comes across as 'gruff', perhaps the receiving person is being too sensitive. I am a sensitive person myself, but I value the words of experts more than my feelings.

Your post was very encouraging to me BDD, especially above where your success/failure ratio as flipped. I hope to one day say the same. One day.

Everyone here has helped encourage me as well, and spur me on to better things. And that includes you BDD. So, thank you.

Lastly, to rehsd, I'm glad your board is working now! It is a good feeling indeed. Sorry for jumping in unexpectedly but BDD's post was too good to pass up.

Chad

Everyone here, I'm sure, is in favour of helpful criticism and input. It would be wrong to suggest otherwise.

Apologies. I was looking at akohlbecker's design. You might be using the same design software but I am often amazed by other people's ingenuity.

Anyhow, now that you've switched from 6502 to 65816 and CPLD, you have enough dormant resources to make a UART. You might need an inverter or want a buffer but it is possible to use 65816 EMU pin for UART transmit. plasmo recommends using 65816 M/X pin for UART transmit and CPLD for framing of 8N1 input.

EMU and M/X pins can also be used for servo control or digital LED control. Meanwhile, unused CPLD cells can be used for potentiometer reading or mouse positioning. See EEVblog #1054 - How an Analog PC Joystick Works for potentiometer. The POKEY chip in an Atari 2600 game console may have similar functionality.

Thanks, it is quite satisfying to optimize a circuit to fill only a limited number of chips, but use every gate available, even though wasted gates don't actually matter that much. A fun challenge!