[Coco] Re: 64K Mode

[John Collyer]

That's true, but it also works on a coco3.  Try it.
Run SuperPatch EDTASM+ on a coco3 emulator
and see if it don't work.  I'll bet it does.

John Collyer

----- Original Message ----- 
From: <jdaggett at gate.net>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Wednesday, January 14, 2004 12:57 PM
Subject: Re: [Coco] Re: 64K Mode


> John
>
> That is what I have been saying. This is for the SAM CHIP ONLY
> COCO 1 and 2 Only
>
> In Memeory Map type 0 (ZERO)
>
> Ram is in the lower 32K and ROM and vectors in the upper 32K.
> With 64K of ram on board,  the Ram is configured as two (2) banks
> of 32K mapped in the lower 32K of the memory map. The "P"
> register controls which page is mapped in.
>
> In Memeory Map Type 1 (ONE)
>
> Ram is configured from address $0000 to $FEFF. The upper 256
> bytes are not accessable as they are I/O and vector sapce.
>
> james
>
>
>
> On 14 Jan 2004 at 10:49, John Collyer wrote:
>
> From:           "John Collyer"
> <johncollyer at zoominternet.net>
> To:             "CoCoList for Color Computer Enthusiasts"
> <coco at maltedmedia.com>
> Subject:        Re: [Coco] Re: 64K Mode
> Date sent:      Wed, 14 Jan 2004 10:49:25 -0500
> Send reply to:  CoCoList for Color Computer Enthusiasts
> <coco at maltedmedia.com>
> <mailto:coco-
> request at maltedmedia.com?subject=unsubscribe>
> <mailto:coco-
> request at maltedmedia.com?subject=subscribe>
>
> > OK, Everyone lets get this correct.  Here are the details:
> >
> > The page number bit, P1 is cleared by BASIC when the computer
> > is turned on.  The effect of P1 set can only be used by a 64K CoCo. A
> > 64K RAM is considered as two 32K pages.  When the page number bit is
> > clear page 0 is the first 32K and page 1 is the upper 32K.  With TY
> > clear (ROM/RAM mode) and the page number bit clear the first 32K RAM
> > occupies addresses $0000 through $7FFF and ROM extends upward from
> > there.  Setting the page number bit results in the upper 32K of RAM,
> > which was not accessible with TY clear, being accessed by addresses
> > $0000 through $7FFF.  This allows you to have two BASIC programs in
> > RAM at the same time. One in Page 0 and the other in page 1.
> >
> > TY | Memory map mode | Set         | Clear
> >                                    $FFDF  | $FFDE
> >
> > P1 | Page Number           | Set         | Clear
> >                                    $FFD5     $FFD4
> >
> > This is how it really works!
> >
> > John Collyer
> >
> >
> >
> > ----- Original Message ----- 
> > From: <jdaggett at gate.net>
> > To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
> > Sent: Tuesday, January 13, 2004 11:35 PM Subject: Re: [Coco] Re: 64K
> > Mode
> >
> >
> > >
> > > What ever.
> > >
> > > Correct I shorted the upper range 16 bytes. $FFF0 is the start of
> > > I/O. The Ram is switched in two banks and are located between $0000
> > > and $7FFF when memory map type 0 is selected.
> > >
> > > The HD63x09 has vector for illegal opcode trap at $FFF0 and
> > > $FFF1. The MC68x09 does not.
> > >
> > > james
> > >
> > > On 13 Jan 2004 at 18:04, Alex wrote:
> > >
> > > From:           Theodore (Alex) Evans
> > > <alxevans at concentric.net>
> > > Subject:        Re: [Coco] Re: 64K Mode
> > > Date sent:      Tue, 13 Jan 2004 18:04:41 -1000
> > > To:             CoCoList for Color Computer Enthusiasts
> > > <coco at maltedmedia.com>
> > > Send reply to:  CoCoList for Color Computer Enthusiasts
> > > <coco at maltedmedia.com>
> > > <mailto:coco-
> > > request at maltedmedia.com?subject=unsubscribe>
> > > <mailto:coco-
> > > request at maltedmedia.com?subject=subscribe>
> > >
> > > > On Jan 13, 2004, at 3:39 PM, jdaggett at gate.net wrote:
> > > >
> > > > > The Sam Chip in the Sam Chip of the CoCo 1/2 hasa two memeory
> > > > > map types
> > > > >
> > > > > Type 0 is ram from $0000 to $7FFF and Rom from $8000 to $FDFF
> > > > > and from $FFF2 to $FFFF.  $FF00 to $FFDF is I/O and $FFE0 to
> > > > > $FFF1 unused.
> > > > >
> > > > > Type 1 is all ram $0000 to $FDFF. $FF00 to $FFDF is I/O and
> > > > > $FFE0 to $FFF1 unused. $FFF2 to $FFFF is ROM and vector
> > > > > location.
> > > >
> > > > I am almost positive that the the area switched extends up to
> > > > $FEFF with only 256 bytes for I/O and vectors.  In fact according
> > > > to some notes that I made a long time ago the destinations for the
> > > > all but one of the 6809 vectors (I don't have a note for the 6309
> > > > unimplemented instruction at $FFF0) lie in in the FE00-$FEFF
> > > > range.  SWI3 pointing to $FEEE, SWI2 to $FEF1, FIRQ to $FEF4, IRQ
> > > > to $FEF7, SWI1 to $FEFA, and NMI to $FEFD with reset being the
> > > > exception which points to $8C1B
> > > >
> > > >
> > > > -- 
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> > > > Coco at maltedmedia.com
> > > > http://five.pairlist.net/mailman/listinfo/coco
> > >
> > >
> > >
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> >
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>
>


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