Several answers (3)
Date: 1998-03-31 19:15:55

Hallo Andre,

Question: is it possible to send me the SCH of your (final) version of the IEEE 
interface for the LPT-port?

> Hm. Not having the symbol on the keyboard doesn't mean not being able
> to produce them.

I thought that I read that somewhere or it was deduction from what I read in 
the well known list of products.

> After all by switching the _charrom_ to graphics mode....

How this is done on the PET? I found out by poking 59468,12. but that 
(certainly) is not the friendly way to do it.

> Hm. 128 chars times 8 bytes per char makes 1k charrom (the 8th bit is 
> inverting the character by hardware) for one character set. 
> 1k fits into a 6308.
> 2k make up the upper/lower and upper/graphics modes, which fits to the
> 6316. 4k (in the 6332) would have the normal us charset (both modes)
> as well as the nationalized in the second half. 

I disagree. 128 ASCII characters PLUS 128 graphic-characters makes 256. Double 
it for inverting makes 512. 512 * 8 = 4096 = 6332.
So only ASCII + invert = 6316.

> But setting it on the nationalized one could probably switch between
> us and nationalized charsets (as the DIN key does in german C128 machines).

I do have a German C128 as well. (They were much  much cheaper then here in the 
Netherlands) And the CHARROM is a 2764 = 8KB in my case!

Other question: The German 8032SK has no @. My oldest son opened the drive 
during the dump  :-(, so I had to start all over again. I could not find @ so I 
had to rename the targetfile. Later I found out that the Beta/Ringel-S replaced 
the @. Is that normal or just the case with the PETs? (My German C128 has a @)

> Can you switch the character sets on the screen to normal (i.e. us) chars?

Not that I know of but 1) how and 2) as I said I have my own opinion about the 
size of the CHARROM.

Hallo Marko,

> Crashing REU...
> Does anyone know what is going on here?  I would investigate this further
> if I had time.

The manual of my REU says:
--- The C128 must be in 1 MHz mode when a DMA transfer is wanted. ---

Sorry for the cripled English but it is a tranlation from German. I think this 
answers all your questions. 

Hallo John,

> I'd investigate if I had an REU.  Does anyone have a spare I could buy?

One of my projects is to find out if I can build an hardware REU-emulator. As I 
understand from earlier emails, you at least made a software emulation. Could 
you give us some details? Is there anybody else who has done some research in 
this area?

> This is the sort of thing a logic analyser should sort out in no time.

I don't think so. You can measure HOW it behaves but that doesn't tell you WHY 
it behaves like that. Interpreting the measured HOW only makes sense if you 
know how it SHOULD behave. Even then there are barriers in the form of black 
boxes. In this case it is meant figuraly as well as literaly (? letterlijk, 
Woertlich). If the output of a black box does not behave as expected with the 
given input, then we either mis-interpreted its function or the damned IC is 
simply damaged ;-)

Groetjes, Ruud

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