Re: PET 2001 Fix....WAS: Will pay good money for NON working PET 2001 motherboard.

From: Marko Mäkelä <>
Date: Tue, 24 Nov 2009 15:27:10 +0200
Message-ID: <20091124132710.GD27442@x60s>
On Tue, Nov 24, 2009 at 07:53:33PM +0900, Philip Lord wrote:
> Just a quick follow up, and a question for the list:
> The original character ROM contains two sets of capital letters, and on 
> set of lower case. Does anyone know why there are two sets of cap  
> letters?

There actually are two 128-char character sets in Commodore 8-bit computers:
uppercase/graphics and lowercase/uppercase.  On models where reverse
characters are not implemented in hardware, the character sets are 256-char,
but the upper half is the same as the lower half, but inverted.

In the home computers (VIC-20 and later), you can switch between these two
character sets by pressing SHIFT and the C= key.  If I remember correctly,
that does not work in the PET.  But these control codes should work:

print chr$(14); rem ctrl-n selects lower/upper-case
print chr$(142); rem shift-ctrl-n selects uppercase/graphics
print chr$(8); rem ctrl-h disables SHIFT+C=
print chr$(9); rem ctrl-i enables SHIFT+C=

Some graphic characters exist (and are identical) in both sets.  These
graphics are what you obtain on the VIC-20 and later when pressing the C=
key together with a letter key.

> Presently I have replaced the lowercase letter set with the new Japanese 
> fonts. Hopefully this was the correct thing to do. A poke 59468,14 should 
> activate them. However you do lose the lowercase characters of course. If 
> you believe I have made a mistake, please let me know.

I am just guessing, but I would expect that the original font preserved
positions 1 to 26 (a to z) intact.  Those would correspond to the lower case
letters in the lower/uppercase character set.  If the Japanese glyphs are
put where the uppercase letters used to be (65 to 138), then it would make
sense to replace the lowercase glyphs with uppercase ones at 1 to 26.

For what it is worth, I found a homebrew EPROM in a VIC-20 that had replaced
some of the C= graphics characters with accented letters.  The official
Swedish/Finnish modification had the chars at [\].


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Received on 2009-11-25 08:30:20

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