Yeah, as Steve said $E880-$E88F (mirrored through $E8FF) is the CRTC in the newer PETs. They simply used the address lines A4 through A7 as chip selects (within the $E8xx range) for the I/O chips (KBD+ PIA, IEEE PIA, VIA and CRTC), which means each chip is only mirrored within that particular address range (unlike the older PETs); the PIAs have positive chip selects which makes it even easier. That leaves E800-E80F (NOT(A4.A5.A6.A7)) available. m ----- Original Message ----- From: "Ethan Dicks" <email@example.com> To: <firstname.lastname@example.org> Sent: Thursday, November 10, 2016 1:53 PM Subject: Re: cbm 8032 io area $e800-$e8ff decoding >I was curious so I checked... > >> I don't see anything at $E800 - $E80F; what uses it, if anything? > > I used TIM on my 2001-N/3032 (no CTRC) to look for locations that > aren't returning "real" values, and I see two places that read back > with a value of $E8 ("dead" locations will read back the upper address > byte). > > $E800-$E80F > $E880-$E88F > > Every other address in the $E800 block read back with some value, with > lots of obvious mirroring. > > I didn't have a handy CTRC machine to run the same check. > > -ethan > > Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing listReceived on 2016-11-10 20:00:02
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