From: André Fachat (afachat_at_gmx.de)
Date: 2007-12-11 23:36:45
Hi Jack,
that's actually a nice idea considering the simplicity of the
interface. The problem is the PET memory map
First you can simply plug the schematics under the PET
CPU, but it needs a chip select line.
I see those options:
1) decode the I/O are $e800-$e80f (other parts of the I/O area
have mirrors of the original ICs, so won't work
2) use the $9xxx or the $Axxx expansion ROM select line
would only work if those are asserted even on write, but I
don't think they are
3) add an own address decoder (maybe like 2 74ALS688 comparators)
to decode an open address space (like $e80x as above,
behind the video RAM, or in the expansion area)
IMHO the 3rd version is always feasible, but needs an extension
of the schematics as it is now
BTW: Jim, can you give a link to your version so I can check?
Thanks
André
-------- Original-Nachricht --------
> Datum: Tue, 11 Dec 2007 15:08:26 -0600
> Von: "Jack Rubin" <jack.rubin@ameritech.net>
> An: cbm-hackers@ling.gu.se
> Betreff: RE: 1541IDE and 1541IDE-S -- and 8250IDE?
> Moving just mildly OT, what would it take to interface this to a CBM/PET
> system?
>
> Jack
>
> > -----Original Message-----
> > From: owner-cbm-hackers@ling.gu.se
> > [mailto:owner-cbm-hackers@ling.gu.se] On Behalf Of Jim Brain
> > Sent: Tuesday, December 11, 2007 2:57 PM
> > To: cbm-hackers@ling.gu.se
> > Subject: Re: (Fwd) RE: 1541IDE and 1541IDE-S
> >
> >
> > silverdr@inet.com.pl wrote:
> > >
> > > On 2007-12-10, at 23:54, Jim Brain wrote:
> > >
> > >> Ruud sent me his schematics, and I am fiddling with them.
> > >>
> > >> However, I didn't get any emails on my offer to design and buy some
> > >> etched boards.
> > >> Just thought I'd check.
> > >
> > > I could do it myself but if you're going to have some
> > available - I'll
> > > buy from you.
> > >
> > >> If no one is interested, I thought I might see if I could extend
> > >> the design to do 16 bit transfers without too many more ICs.
> > >
> > > Sure! That's a very natural (and good) extension of Ruud's idea.
> > >
> > I believe I have a design that retains source compatibility
> > with Ruud's
> > project, but it'd be nice if others could look the logic over
> > and verify
> > it, since I don't do 6502 interfacing projects a lot.
> >
> > The changes I made were:
> >
> > * I mapped the IDE to A4,A3,A2,A1 (instead of Ruud's A3,A2,A1,A0)
> > leaving A0 as the hi/lo byte select
> > * I added another '139, half of which is used to further constrain
> > the onboard CS line so that the IDE lines are only
> > active when A0
> > is low.
> > * I added 2 '573s, in both directions, used as a staging area for
> > the hi byte of the IDE databus
> > * The other half of the '139 is used to select one of 4 operations
> > for the '573s:
> > o During Read and A0 is low, we are reading from
> > IDE, so store
> > hi byte in 573
> > o During Write and A0 is low, we are sending to
> > IDE, so output
> > hi byte on IDE bus
> > o During Read and A0 high, we are reading from 573,
> > so output
> > 573 on 6502 bus
> > o During Write and A0 high, we are writing to 573, so store
> > data into 573
> > * I used a 74LS02 to constrain CLK lines into the 573s with Phi2.
> > * Due to this design, order of access is very important.
> > Reads must
> > always start with low byte, writes must always start
> > with hi byte.
> > * Finished board fits on 2.6" by 3.6". and 9 will fit on
> > an 8x11 panel.
> > * If additional '139, '02, and '573s are not populated, circuit
> > approximates Ruud's original (addresses being shifted)
> >
> > Total circuit takes 7 ICs (244,245,139,139,573,573,02), an IDE
> > connector, and a half dozen passives.
> >
> > As always, comments and help appreciated. If people can
> > either verify
> > my design would work, (or verify that it won't, so I'll need to use
> > Ruud's original design), I can probably spin the boards this week.
> > Christmas presents for folks.
> >
> > Jim
> >
> >
> > Message was sent through the cbm-hackers mailing list
> >
> > No virus found in this incoming message.
> > Checked by AVG Free Edition.
> > Version: 7.5.503 / Virus Database: 269.17.0/1180 - Release
> > Date: 12/10/2007 2:51 PM
> >
> >
>
> No virus found in this outgoing message.
> Checked by AVG Free Edition.
> Version: 7.5.503 / Virus Database: 269.17.0/1180 - Release Date:
> 12/10/2007 2:51 PM
>
>
>
> Message was sent through the cbm-hackers mailing list
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