by Roland Schol » Sat, 27 Sep 1997 04:00:00
Hello out there,
yesterday I blew up the MMU PAL16L8 chip in my ATARI 800XL. (silly boy)
Does anyone have an *exact* decription of that chip or, even better,
a JEDEC Fusemap, so that I could burn a new GAL or PAL?
Thanks,
Roland
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Roland Scholz
University of Koblenz
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Howdy Folks
Some of you guys where asking what the FREDDY chip does. Well, I asked this
Kaj De Vos some time ago, and here is what he had to say.
__________________________________
Message: 239 (#6899)
Title: MMU/Freddy
Author: Kaj de Vos
To: Mathy Van.Nisselroy
Posted: Tue 2-Mar-93 at 9:38:10pm
Replies: 0
Origin: Kaj's Pro Point
Enschede, The Netherlands
Hi Mathy,
The MMU chip divides memory into 2K blocks and decides which part of memory,
RAM, ROM or I/O chips to activate during a read or write cycle of the CPU. It's
also capable of making the self test ROM appear in the 2K window from address
$5000 to address $57FF, while it's physically stored in the ROM chip at $D000
to $D7FF - which in turn is where the I/O chips appear.
Freddy does the work of several smaller chips in older models and controls the
extra memory in the 130XE. So, it divides the extra RAM memory into 16K blocks,
and decides which one should appear at the window from $4000 to $7FFF.
Kaj
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Kaj will join us here in a sort while, he's the techno dude, so don't ask me.
Your noble survant
Mathy Van Nisselroy
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