Subject: Re: Apple II/e newbie - please help
Newsgroups: comp.sys.apple2
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From: david@uow.edu.au (David Wilson)
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Date: 11 Jul 2000 09:46:52 +1000
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processoroverclocked@33mhz.cjb.net (Jon Bettencourt) writes:
>PR#3 is an output remapping command. By typing PR#3 you are remapping
>output to the card in the auxilary slot (in this case an 80-column card).
>All it actually does is call location $C300, where the card's ROM starts.

Strictly speaking PR#3 does not call $C300. All it does is place $C300 in the
character output vector. The first character that is output after the PR#3
command will cause a JSR to $C300 (the init entry point to the 80 col card
firmware). The 80 col firmware will then change the output vector to point to
$C307 (BASICOUT) and the input vector to $C305 (BASICIN).
--
David Wilson  School of IT & CS, Uni of Wollongong, Australia