[Coco] Re: 64K Mode

[John Collyer]

As a matter of fact, this is how SuperPatch EDTASM+ works.
That how come you can have almost a 64K buffer area for
program source code.  SuperPatch EDTASM+ turns on/off
ROM as it is needed by writing to $FFDF/$FFDE.  Check
it out at my coco page.  You can get SuperPatch EDTASM+
there.

John Collyer

----- Original Message ----- 
From: "John Collyer" <johncollyer at zoominternet.net>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Wednesday, January 14, 2004 10:49 AM
Subject: Re: [Coco] Re: 64K Mode


> 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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