Re: Several answers (2)

From: Andre Fachat (a.fachat_at_physik.tu-chemnitz.de)
Date: 1998-03-28 14:37:23

rbaltiss@worldaccess.nl wrote:
> If I were making one from scratch, I'd probably wire a 6551 onto an adapter
> board and stick it in a ROM socket with little or no decoding.  Only when

You better use the 16550A with FIFO or use a hardware generated RTS line.

> I have a dream for my Portmaker: in my copious free time, port the C64 PPP
> stack to the PET and hook my PET up to the Internet.  If only someone made
> an Ethernet card that was easy to hook up to a 6502...

What C64 PPP stack? I only know of two SLIP stacks (mine and Daniel Dallmanns).
It would certainly work with a 8x96 and my OS/A65 (enough memory...)
but for the 8032, uh, you would have to reduce functionality a lot
if you want to fit the OS + SLIP stack into RAM.

> > where the drawing color is not transparent? Netscape prints transparent
> The 3008 is generated by Marko and is just a 2-color GIF-file as is the 8032. I 
> noticed these problems with the GIFs of the 1541s working with NS on HP-Unix. 
> After downloading them I had no problem printing them on my PC.
Well, I had... :-(

> This is a point of confusion for me as well. I never saw a 4032 so I don't know 
> for sure how they look like. But I thought they looked like a square 8032. 

They do. We had one at school, 12" display, graphics keyboard.
We also had a 8032SK (and a 3032, 9", graphics keyboard).

> received SCHs from Chris Happe (Canada) for the 4032/8032.  These  apply IMHO 
> to the boards used in the 8032SK as they have all those wires and markings 
> reffering to 40 and 80 columns.
Are they original? Are they copyable so that I could probably scan them?

> > Ruud, are you sure that in your PET 3008 schematics PIA1 CB1 as well
> > as VIA PB5 are connected to VIDON,
> YES
What I meant is that PIA1 CB1 generates the system interrupt, so I thought
it would be connected to the vertical sync (TVV, not VIDON).
Also the VIA PB5 is normally (i.e. in old PETs) used to check if the
electron beam is off-screen so you could access memory without 
snow. [see below for solution!]
> 
> > which is controlled by PIA1 CA2?
> CA2 controls the graphic-mode. (For those who don't know the PET, graphic-mode 
> = using "funny" characters in stead of ASCCI. On the C64 you use the shift key 
> for this. The PET has no real grphic capabilities at all.)
You mean VIA CA2? This switches between text (upper/lower case characters)
and graphics (upper case/block graphics characters) mode.

PIA2 CA2 controls IEEE488 EOI and is (on older PETs, according to Larry
only with the first type of board) used to blank the screen completely.

> > I assume the two should be connected to TVV (vertical sync), right?
> 3008 NO, For the 8032, 8032SK and 4032 YES. (4032: see remark above)

Ok, I just had a look at the schematics and I see the problem:
According to your schematics
VIDON is connected to PIA1 CA2 (which is output and controls EOI) _and_
to the output of UH10D. Is this correct?

I think I get what it's all about: on the non-CRTC
controllers the _logic-generated_ VIDON signal produced the IRQ signal
and was used for VIA PB5 (offscreen check). With the CRTC PETs this
signal is not available anymore (well it is, 6545 DE - display enable,
but CBM didn't use it here), so I guess they replaced it with
the vertical sync signal at least on PIA1 CB1 to generate the system
interrupt (is it also replaced on VIA PB5? the 8032 schematics suggest so)

This still leaves the question of PIA1 CA2. It controls IEEE488 EOI,
and on first board PETs it also controlled the screen output (let's
call it VIDEN for video enable). Larry wrote it's only the first-type
PET, which means it has no connection to the video stuff in the 3008.
So I assume it is a bug in the schematics, as in the 3008 the
VIDON is logic-generated?

Thanks to all that answered, and sorry about being a bit picky, but
I want to make VICE as good as possible and also fix the information
in my petindex.

Thanks again
Andre

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Andre Fachat, Institute of physics, Technische Universitšt Chemnitz, FRG
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