Thank you Garth, and thank you BDD!

Edit: I just switched it to the BDD method, used an extra NAND gate that I had laying around anyways!

For simplicity, you might want to pick up one of these:



You simply wire it up to a UART as a 5-wire interface and plug it into a USB port on any computer. It configures as a com port on Windows, OSX or Linux and just works.

And yes, if you can, start with a UART and get a simple working system first, get a decent monitor setup and then start adding I/O devices.

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

Wow, that's awesome, it's seriously an all-in-one package deal. Very nice, thank you for that link.

And yes, start with one thing, then to the next and the next. Good plan. Thank you again.

I've used that one for a portable interface when prototyping... very convenient. On my last Pocket SBC I used their DB9-USB interface:



These mount as a standard DB9 connector (male or female versions) and have interface voltage levels of 3.3V, 5.0V or 12V (RS-232). I'm using the 5V and 3.3V Male versions on my current setups. They cost more (sadly) but they are excellent interfaces.

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

I've been lookin' at the 74HC682 as part of a 2-chip jumper configurable decoder + glue logic solution (including four I/O device select outputs)... Compared to the 74HC688 it has an additional active low P>Q output that I use to drive both the active low FLASH ROM /CE input and the active high SRAM CS2 input. While RAM or ROM is selected every clock cycle, half of a 74HC139 decoder is used to route PHI2 qualified /MRD and /MWR signals to memory only during clock cycles with an address above or below the I/O page address. The other half of the 74HC139 is used to provide four I/O strobes spanning the I/O page for peripheral ICs.

Good luck on your project.

Cheerful regards, Mike, K8LH

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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?

Too bad they picked the Pentium 4 which is considered by many to be the dog of the family.

If you do get it, I may ask that you to perform a test to determine whether the floppy controller can handle single density formats.

_________________
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?

floobydust,

So correct me if I'm wrong, but this is how I see those components being used (I use Linux, not sure if you are familiar with that side of things):

1) I plug a USB port from my computer into the DS_LC234X. Linux automatically sees "/dev/ttyUSB0" is a serial port. (I believe all the FTDI drivers are built in now, if not download/install.)

2) I plug/solder the DS_LC234X into a 6551 ACIA or something similar, which would then go to the 6502.

3) Use Linux terminal and/or additional software to send/receive serial data through "/dev/ttyUSB0".

Am I understanding this correctly?

Essentially, yes.

Any cheap USB serial device will work. Just ebay/amazon for one. the serarch term is usualy USB TTL SERIAL.

I use generic ones which are under £10 when I don't care. Some have it all built into the USB plug too with just flying leads for Tx, Rx, 5v and Gnd.
e.g.

https://www.amazon.co.uk/FT232RL-Adapte ... B083LLPY9G

Linux (which I use) supports them all and has done for many years now - some appear as /dev/ttyUSBx and some as /dev/ttyACMx. Technically there is a difference but they all work the same from a serial port point of view. Then minicom, Putty, etc. on the Linux side as your terminal.

-Gordon

_________________
--
Gordon Henderson.
See my Ruby 6502 and 65816 SBC projects here: https://projects.drogon.net/ruby/

Thank you Gordon, that is good to hear.

I'll be making changes and posting a newer schematic sometime soon, when I get time. Might just be including a 6551 now as well. And of course, I'll be considering the feature creep.

Thank you all!

Having found the Xmit bug in the recently released W65C51 ACIA, I wouldn't recommend using one. You can likely find some older Rockwell R65C51 parts if you shop around, if you're really set on using one. I'd suggest one of the newer NXP parts, like the SC28L92 or if you prefer a DIP component, look for the older SCC2691. These are fairly easy to get working, plus there's code around that takes full advantage of them already. No need to reinvent the wheel

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

https://www.nxp.com/docs/en/data-sheet/SCC2691.pdf

That is a beautiful IC, wow so cool. I'll be reading more about this one specifically.

Thank you!

This is an excerpt from Garth's RS-232 Primer page:

"We should mention that although UARTs are mentioned throughout this introduction, it is possible (as you probably already figured out) to do the UART job in software, doing what we call "bit-banging" with individual parallel port bits of I/O ICs like the 6522. "Bit-banging" is where the software handles the shifting, timing, error-checking, etc., instead of letting a UART do it in its hardware shift registers, timers, counters, and other circuits. I believe the Commodore 64 did it with a 6526 (which is a general parallel-I/O IC). This should only be considered a last resort however. (There is a forum topic here on bit-banging 57,600bps on a 1MHz 6502.) Using a real UART is much easier from the programming perspective, usually allows higher speeds, and allows the processor to work on other things between byte transmissions or receptions. Don't confuse asynchronous serial (like RS-232) and synchronous serial (like SPI, Microwire, and I²C). Synchronous serial interfaces with their separate clock line usually do not have the tight timing requirements that RS-232 does, so they're much easier to bit-bang if you have to, and to do so at comparatively high speeds. "

http://wilsonminesco.com/RS-232/RS-232primer.html

I've been thinking it over and over and last night while lying in bed I had an idea to 'bit-bang' UART with a 6522. Why COULDN'T it be done? After researching this morning, I find that Garth mentioned it, and some other places on the net have as well.

In an effort to reduce chip count, board size, cost, and overall complexity, is it possible to use UART on a 6522? Yes, with a low baud rate. And yes, I will probably need some 1-2 MHz oscillator can that would effectively divide for said low baud rate. I was going to run a 1 MHz clock anyways. This is just for talking back and forth with my Linux box, nothing fancy here, no high speeds needed. This is still assuming I'd be using floobydust's suggestion to use something like this:

https://protosupplies.com/product/ft232 ... e-adapter/

Thoughts? I know y'all are professionals, but I gotta start small. I'm already going to be including the 6522 so why not multi-purpose the thing?

Thank you all.

Having done this, I can tell you it's not impossible but it is a bit tricky (certainly a lot more so than bitbanging SPI).

Also, to receive and transmit properly, the bitbang code will probably need the CPU's full attention (unless you undertake the additional challenge of making it run in the background, driven by periodic interrupts). That means the CPU will be unable to do anything else during the time it's transmitting a character, or listening to see if there's a character to receive.

If that tradeoff seems acceptable then maybe the bitbang approach is a good choice for you.

-- 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