65C22 Schematics

cb meeks

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Sep 13, 2018, 3:32:10 PM9/13/18

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A while back, I put a 65C22 on a prototype board (for my IIe) and used it for some blinky lights. Mainly to see if I would have any problems building a real board.

And yes, I had problems. The problem is that it worked, usually. But not 100%. I never did figure out why.

I lost interest and put the prototype away. I no longer have it so I can't remember what all I did.

I asked around at the time and some people suggested that it could be because of using the CMOS version of the 6522. But that's all I can remember.

Anyway, I'd like to get that going again. Something really simple (and stable!). Before I start, are there any schematics around for just a simple 65C22? IIRC, I think I literally just had it wired directly into the appropriate pins with a decoupling capacitor and not much else.

The purpose is to learn from my mistakes and learn how to make a stable prototype card that might, eventually, be something more useful than an I/O chip.

BTW...I had also created a crude serial card that used the 65C51. Again, it worked sometimes and sometimes not.

So I obviously need some guidance. I figure the 65C22 is about as simple of an upgrade as you can get.

Thanks for any pointers!

Ralf Kiefer

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Sep 13, 2018, 6:26:52 PM9/13/18

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cb meeks wrote:

> I lost interest and put the prototype away. I no longer have it so I
>can't remember what all I did.

Read your thread at 6502.org :-)

> I asked around at the time and some people suggested that it could be
>because of using the CMOS version of the 6522. But that's all I can
>remember.

I don't beleave that.

> Anyway, I'd like to get that going again. Something really simple (and
> stable!). Before I start, are there any schematics around for just a
> simple 65C22?

The German magazine c't published their own Applebus card with two 6522.
http://www.appleii-box.de/H056_2x6522VIAat%20the%20Apple.htm

I bought two of them and I used 6522 and 65C22. There was no functional
difference. But I did this in the 1980s. Your 65C22 are younger.

I used two cards for high speed parallel communication between two Apple
II.

Probably this card published by the magazine c't was a clone of another
card. Later I got the same card built in Taiwan. Or probably this was
the clone. Doesn't matter. This card works.

> BTW...I had also created a crude serial card that used the 65C51. Again,
>it worked sometimes and sometimes not.

Modern 65C51 are problematic. See 6502.org.

Regards
Ralf

Michael Black

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Sep 13, 2018, 7:41:50 PM9/13/18

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On Thu, 13 Sep 2018, cb meeks wrote:

> A while back, I put a 65C22 on a prototype board (for my IIe) and used
> it for some blinky lights. Mainly to see if I would have any problems
> building a real board.
>
> And yes, I had problems. The problem is that it worked, usually. But
> not 100%. I never did figure out why.
>

Did it work with a 6522?

In Kilobaud though I can't remember the year or month, there was a column,
I think about troubleshooting, and a month or two was dedicated to Apple
II I/O. And something about the Apple II bus was "odd" and there were
glitches with the 6522. I can't remember details, but I think the problem
was a wrong phase was brought to the bus. Maybe someone else remembers
details, I don't think this was the only place it was written about.

Michael

cb meeks

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Sep 14, 2018, 8:42:05 AM9/14/18

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On Thursday, September 13, 2018 at 6:26:52 PM UTC-4, Ralf Kiefer wrote:
> cb meeks wrote:
>
> > I lost interest and put the prototype away. I no longer have it so I
> >can't remember what all I did.
>
> Read your thread at 6502.org :-)

Oh yeah!! I forgot I asked there too. LOL

> The German magazine c't published their own Applebus card with two 6522.
> http://www.appleii-box.de/H056_2x6522VIAat%20the%20Apple.htm
>

That was very helpful! I don't speak (or read) German but good thing schematics are universal. :-)

It seems the answer is altering the clock somehow (through delays). I've seen several different versions of this. I also noticed they didn't use any buffers on the databus. Other designs do, some don't. What are your thoughts on that?

> I bought two of them and I used 6522 and 65C22. There was no functional
> difference. But I did this in the 1980s. Your 65C22 are younger.
>
> I used two cards for high speed parallel communication between two Apple
> II.
>

That sounds interesting! Would love to know more about that setup. Did you write some custom software to transfer data?

>
> > BTW...I had also created a crude serial card that used the 65C51. Again,
> >it worked sometimes and sometimes not.
>
> Modern 65C51 are problematic. See 6502.org.

Yep. That's correct. I've since started learning another UART (actually, DUART) from NXP.

>
>
> Regards
> Ralf

Thanks!

Ralf Kiefer

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Sep 14, 2018, 9:14:43 AM9/14/18

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cb meeks wrote:

> That was very helpful! I don't speak (or read) German but good thing
>schematics are universal. :-)

Doesn't matter. The schematics and figures are important.

> It seems the answer is altering the clock somehow (through delays).

Just delay PHI0. At the 6502.org thread somebody mentioned the Apple
"Tech Info Library Article 494" from 1984 (last changed 1997). This
solution is a bit different but the result is similiar.

> I also noticed they didn't use any buffers on the databus.

That's not necessary if you add just one or two 6522. Adding some more
peripheral chips I would add a buffer too.

> What are your thoughts on that?

This 65(C)22 card works :-) I added one to my IIe Rev.A and the other
into a Taiwan clone IIeuroplus without any problem.

> That sounds interesting! Would love to know more about that setup. Did
> you write some custom software to transfer data?

The IIe was my master p-System machine. The other was the slave. The
BIOS gave some jobs to the slave because lack of slots, lack of CPU
power, ... The communication was like the Centronics protocoll because
the 6522 can do this well. I used both parallel channels for each
direction.

The slave was populated by a clock card, 512kB RAM card, PAL card. And
there were plans to do more.

Regards
Ralf

cb meeks

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Sep 14, 2018, 10:04:36 AM9/14/18

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After some more research (and perhaps, a little better understanding of the problem), I think I will try the Apple Hardware Notes solution over the German one. The German one seems to be more analog in nature.

This one,

https://ia801004.us.archive.org/18/items/Apple_II_HW_6522_VIA/Apple_II_HW_6522_VIA.pdf

seems a little more digital in nature and easier for my simple brain to understand. However, I'm quite the n00b so I could be way off base here.

Charlie

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Sep 14, 2018, 1:52:08 PM9/14/18

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Have you looked at "the custom apple & OTHER MYSTERIES"?
Chapter one has information on the 6522.

https://archive.org/details/hofacker-floegel1982-the-custom-apple

Charlie

cb meeks

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Sep 14, 2018, 2:25:43 PM9/14/18

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No, but I will! Where was that book my whole life? It looks amazing.

Thanks for the reference!

In fact, does anyone have a hard copy they could part with? I like having the physical books.

Thanks again.

Michael J. Mahon

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Sep 15, 2018, 2:50:42 AM9/15/18

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The Mockingboard is a popular example of a card that interfaces two 6522s
to the Apple bus.

It uses an RC delay network followed by some thresholding to square up the
leading edge. The approach is apparently fairly robust, since the card and
its clones are widely successful. Schematics are available on the Web.

I believe that the early John Bell dual 6522 card, with four 8-bit parallel
ports, also used an RC network to delay the clock.

--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com

cb meeks

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Sep 17, 2018, 10:37:55 AM9/17/18

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I actually built a Mockingboard clone on a breadboard a few years ago. Then, sometime later I tried to make a more permanent version on proto-boards. I never could get it to work. I think my error was in the way I built the RC network for the clock. I didn't understand much about it then (still not very clear on how RC networks work).

But recently, I've learned more about how the timing works in relation to the 6522 so hopefully, I can get something going soon.

Scott Alfter

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Sep 17, 2018, 1:27:49 PM9/17/18

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In article <1ff0d1ac-923f-4a34...@googlegroups.com>,

cb meeks <cbm...@gmail.com> wrote:
>Anyway, I'd like to get that going again. Something really simple (and
>stable!). Before I start, are there any schematics around for just a
>simple 65C22? IIRC, I think I literally just had it wired directly into
>the appropriate pins with a decoupling capacitor and not much else.

After going through this thread and reading a few other sources, I knocked
this design together:

https://gitlab.com/salfter/a2gpio

(also at https://hackaday.io/project/161297-apple-ii-dual-6522-gpio-card)

It's a reimplementation of the c't dual-6522 board, with the four control
lines of each 6522 also brought out to header pins and the inverter-based
clock delay replaced with the flip-flop-based design that was recommended by
Apple for this purpose.

I haven't had anything produced yet, but all the information needed to order
boards and parts is in there. You could have the bare boards made for about
$10, shipped, and the remaining components might cost $20 or so (the 6522s
are the most expensive part, at $7 each from Mouser for the W65C22S or
W65C22N).

_/_
/ v \ Scott Alfter (remove the obvious to send mail)
(IIGS( https://alfter.us/ Top-posting!
\_^_/ >What's the most annoying thing on Usenet?

cb meeks

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Sep 17, 2018, 1:33:13 PM9/17/18

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Thanks for doing this! I think this will be a great foundation for me to build on.