For anyone else, like me, who likes to see all this stuff visually, here is a diagram (of the whole memory map) I made so I could visualise what was going on. The coloured blocks are the addresses of the devices that are selected. The red entries are the ones that only have one device selected ...

It’s neat to see test driven development of logic circuits, that’s a pretty good tool.

ok.. I have made some progress. I was treating /WE as active high, not active low. once I changed that, I got a different behavior from the ready pin. not working still, but think i'm on the right track. (and time to read the data sheet again)

Tagging onto this thread in hopes of also getting the SN76489 working. I've got mine connected to a VIA, and while ignoring the ready pin, I've managed to get it muted, then produce a sound! Now that it's working, I wanted to try and do it the "right" way and read the ready pin. I've got it tied ...

I just ripped it out. I was scratching my head about increasingly rudimentary code, off and on for weeks. That should have been my first clue. I had it rebuilt from scratch in about 20 minutes and the test worked right away. Lesson learned!

ok, well perhaps I should have tried this earlier. I just ripped the circuit out, and built it again. and of course, IT WORKS. I thought I was going nuts, trying to get a dead simple program working, when it was the wiring that was at fault. In any case, thanks for taking a look.

As a debugging step, I setup port B on the VIA as a debugging output and connected LEDs. I also setup port a pin 0 as an output. In my interrupt handler, I first pulse port a pin 0, and then load ACIA_DATA and output it on port b.

When I power up, and hit '1' on my terminal window, what I'm seeing ...

That TxD line may be a red herring. I tried my test again, hitting '1' instead of 'Q'. The scope shows I sent '1' but received the same shape of pulses. So I was maybe just seeing things there.

I did change the handler to immediately do a "sta ACIA_DATA" and it looks like it does do this from the scope, it's just not being decoded correctly? Looks like its slightly delayed.

It does feel like I'm at the 90% mark on this milestone.

Here's a hex dump of the binary (I'm always amused after spending so much time on something only to see a few kilobytes of data)

00000000 a2 ff 9a 20 71 80 20 4e 80 a9 24 20 cb 80 a9 00 |... q. N..$ ....|
00000010 8d 01 44 a9 09 8d 02 44 a9 ...

I've been spinning my wheels on this for too long and thought I'd ask for help here. I am probably missing something simple. First, I'm a Mac user. I have a MacBook with a USB-TTL adapter based on FT232R. I have it in 5V mode.

Adapter is this: DSD TECGH SH-U09C5 USB to TTL UART Converter
ACIA is a ...

Hello,

My interest in computers started with a 200-in-1 electronics kit from Radio Shack, which started me down the path of electronics and the "Engineer's Notebook" series, and eventually being on a first name basis with the staff at RS. This was coupled with getting a Commodore 64. I had the ...

For reset, I'd like to actually experiment with a DS1233 (and the required caps/resistors) - not quite as convenient as the DS1813 but it's accessible from Jameco, so an easy recommendation to cart for anyone who is planning to buy the Ben kit.

What’s needed around the DS1233? I’ve been looking ...

I am one of those builders.

I stumbled upon his videos, and it rekindled an old curiosity. I think the videos have their place -- they are uncluttered and are just enough to get going. I randomly found them, and they inspired me, and it eventually led me to forums where far more advanced topics are ...