[Coco] 6309 microprocessor project 01-28-2004

[John Collyer]

Because the size of this project, and the fact that I wanted to support the
Multi-Pak Interface.
I have dropped the Memory Management Extension Register support for 16MB.
This opens
the area in the memory map for other things.  Since OS9 and NitrOS9 only
supports 2 MB.
My emulator will only support the 2MB limit making the addresses from
$FF70 - $FF7E
open and available to the routines which other programs can call to link in
devices to FFxxH.

How the Multi-Pak and Switched Bank ROM/RAM works:

You can have a maximum of two switched banked rom/ram cartridges. The
Multi-pak memory
is a table of four 16K/32K memory pointers to a 16K/32K memory area.  Inside
of singlebank
and fixbanks the Multi-pak memory pointers are updated.  The functions
singlebank and fixbanks
use the fact that, if 16K/32K external ROM mapping, the table of virtual
memory pointers are
updated with the pre-calculated Multi-pak memory pointer. On startup the
slot select value uses
the slot select switch on the Multi-pak for its startup state. Inside of
$FF7F register the slot select
value is written and fixbanks is called to update the memory pointers.  The
functions singlebank
and fixbanks do not care about the banked rom/ram.  Other routines take care
of switching the
pointers for the switched banked rom/ram.

John Collyer

----- Original Message ----- 
From: "John Collyer" <johncollyer at zoominternet.net>
To: <coco at maltedmedia.com>
Sent: Wednesday, January 28, 2004 11:10 AM
Subject: [Coco] 6309 microprocessor project 01-28-2004


> 6309 microprocessor project:
>
> Hello,
>
> I am working in the memory part of the program, and I added support $FF7F
> Multi-Pak Interface Register.
> There are four slots and each slot can be either 16K or 32K external rom.
> Of course this means that now
> I am supporting (Paul T. Barton's NoCan 16MB Interface.)  Instead of the
MMU
> extension registers being
> located at $FF70-$FF7F they are now located at the NoCan locations
> $FF80-$FF8F.
>
> I would also like to add support for banked switch 16K or 32K rom
> cartridges.  I not sure how to do this,
> but I have eight 16K banks and eight 32K banks.  I think I'll need a flag
to
> let me know this is a banked
> switched rom and monitor $FF40 FDC register for any write page number
> requests.
>
>
> John Collyer
>
>
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>