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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?

Sounds sensible. The VIA timers are pretty easy to use when you get your head around the latching, and you can still either poll for them to complete or use interrupts. In addition to Garth's links there are a few simple examples here: http://www.6502.org/source/io/6522timr.htm (though there's a bug in the Timer 1 one-shot example, can you spot it?)

_________________
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?

Hey! I found the datasheet for my G65SC02 in the 6502.org documents archive while I was poking around looking for delay and timer stuff. (I wonder how come Google doesn't know it's in there?) Looks like it does support the "new" instructions. Hooray!

Edit: LOL, I see Garth already posted a link to the very PDF I'm looking at.

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"The key is not to let the hardware sense any fear." - Radical Brad

Is the bug that the text seems to suggest the two routines are different, when they're exactly the same except for the last instruction? (Which the text seems to suggest should be the same when it says "The rest of the program is identical.")

Edit: (I'm guessing, more specifically, that that last instruction should be a read from the low order counter, just like for Timer 2, in order to clear the interrupt flag.)

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"The key is not to let the hardware sense any fear." - Radical Brad

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

_________________
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?

The bug I saw was that it's still testing bit 5 of the IFR, which is Timer 2's bit - it should be testing bit 6, i.e. "LDA $40" or by using BVS.

As you spotted though, it's also reading the wrong register to clear the interrupt flag. It can be confusing which registers and operations do or don't clear the flag, and it may be simpler to just write to the IFR to clear it, given that the right data ($40) would already be in the accumulator in this case.

Thanks Garth for posting Bruce's delay code. That really is very slick: the effect of nested loops without any nesting.

Cool story! That pretty much nails the difference, I think. Jazz musicians find that lack of structure freeing and even exhilarating. There used to more improvisation in classical music, but nowadays mostly only baroque keyboard players learn to do it. It's a shame we've let those skills fade!



Yeah. I stared at those 4 instructions for a LONG time yesterday.

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"The key is not to let the hardware sense any fear." - Radical Brad

The module with the integrated breadboard in the photo upthread is called an "RC6502 Project Platform." Since my LCD is now working properly, I wanted to get it off the breadboard, giving it a more permanent home, and freeing up breadboard space for the next project (keyboard interface).

At some point (I think because PCBWAY gave me a coupon), I ordered a whole stack of RC6502 prototyping boards. These are just plated through hole perf board with the RC6502 bus along the bottom edge, a VCC rail up the left side, a GND rail across the top, and a "custom bus" down the right side. I figured this would be a good place to build an LCD board for Blue April. This did not go well. Turns out I had the wrong kind of wire, the wrong kind of solder, and the wrong kind of IC sockets. After several false starts, ruining several of the prototyping boards (no big deal, I have 10 of them!) and melting some IC sockets (no big deal, they're cheap) yesterday I plugged in the third try, and saw "OK" flash up on the LCD. I have to say, in spite of all that frustration (or maybe because of it), the sense of triumph for completing this relatively standard and straightforward project was very satisfying.

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"The key is not to let the hardware sense any fear." - Radical Brad

Looks great! That's how I started soldering too: the hard way. You learn more from mistakes, so that will pay off in the future for sure. It looks good, and functions well!

For the keyboard interface, have you watched the Ben Eater series on PS/2 keyboard interfacing? I really liked his videos, and I used them to model my own keyboard interface.

What's next after keyboard? VGA display?

Chad

I find that soldering wires to things (IC socket pins, for example) is much trickier than soldering things onto PCBs. Wire wrap is much to be preferred; unfortunately I didn't have the right IC sockets for wire wrap, so I had to do a kind of hybrid (wire wrap on one end, solder on the other). Someone in a different thread recently posted a link to Phoenix Enterprises; they seem to have a nice selection of wire wrap sockets at affordable prices. Dunno why they didn't come up in my google searching. Anyway, I'll stock up on them for the next thing.



I have, and as you say, I plan to use them as the starting point for my own interface.



Definitely video, but I think not VGA. Real VGA seems like pie-in-the-sky to me; the VGA implementations I know of either use modern microcontrollers (which I want to avoid) or use acres of breadboards / logic chips. I also don't want to do a kind of crippled VGA like Ben Eater's "worst video card in the world."

I have some interesting old CRT controller chips (Hitachi "6845s", Intel 8275) and Gerry Kane's "CRT Controller Handbook." What I'd like to do is make a true retro-style composite video out using one of those. I like the idea of making, basically, a terminal emulation board with powerful text capability (the 8275 should be particularly good for this) without worrying about graphics / sprites / colors and so on. There is a VDU board for the RC6502, but it's based on the 6847, which I don't have a spare of, and which I dislike a bit, from using it in my CoCo2.

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"The key is not to let the hardware sense any fear." - Radical Brad

If you are ok using those kinds of chips, all the better. Everyone has a particular flavor they are comfortable with. I'm sure you have heard from George (gfoot), he is kind of like my 'video expert', and he has Youtube videos on different variations/chips he has used to generate video signal.

But like you are saying, if you are going to "do it right" you shouldn't settle for a crippled version. Maybe as a stepping stone though? My first TTL VGA used only 4 colors, now I'm playing with 16. That isn't the biggest upgrade, but getting something onto the monitor is step 1. Making it functional is step 2.

Thanks!

Chad

I'm getting some unexpected interrupt behavior - specifically, constantly spamming of interrupts.

Currently, I have things wired up like this:



VIA1 is on the LCD board; it isn't generating any interrupts, but I did wire up it's IRQ pin to the bus (don't know why I did that).

VIA0 is on my prototyping board; I want it to generate an interrupt when CA1 transitions. In the long run I want to use it to generate keyboard interrupts, but for now a momentary push-button will be fine. Before I start blaming my software, I want to make sure I understand how the hardware works.

I read in the Primer that you can't wire-or multiple 'S' version VIAs together to have multiple interrupt source, which appears to be what I've done. However, only VIA0 needs to actually generate interrupts, so, in a pinch, I can just cut the IRQ line on the LCD board if that's what's causing the problem.

However, it seems like what's described in the primer is that when two 'S' VIAs are wire-ored together, VIA0 will try to pull IRQ low, but VIA1 will keep it high, preventing the interrupt form being issued. IOW, I'd expect to see *NO* interrupts; instead I have the opposite problem - constant interrupts! This happens even if CA1 isn't hooked up to anything.

I want to double-check my understanding before I start cutting wires.

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"The key is not to let the hardware sense any fear." - Radical Brad