[Coco] Re: Coco Repack

[Kevin Diggs]

James,

	What about altering the page size? What are your thoughts?

					kevin

jdaggett at gate.net wrote:

> 

> Mark

> 

> The MMU is real simple. It is basically a 2 to 1 4 bit wide multiplexor that feeds a

> 16x8 ram. The GIME chip uses a 16x6 ram. Most  likely the package was limited to

> 68 pins by Tandy and cost factors. Next standard size up is 84 pins in a PLCC

> package. Given that during the 80's it was around 10 cents a pin for package cost,

> another 16 pins would have meant another $1.60 for the part.

> 

> I really believe that many of the limitations of the GIME chip is solely due to keeping

> costs to a bare minimum.

> 

> The VGA portion is tough to code and will occ py the most territory. That will

> determine how big the FPGA is and how much any project like th is will eventually

> cost. Most of the free VGA cores are more modern and do not cover CGA

> resolutions. Or they are very generic and need more work to make them compatible

> to 8 bit buss. One of the nice things is that the software to design the logic and

> program the FPGA is free. Right now I am designing the logic for the two registers

> at $FF92/3. These registers do a dual purpose. They enable interrputs and also act

> as interrupt flags. When you read the register, the flags are cleared while the

> interrupt remains enabled. Not a simple D-FlipFlop latch. Most of the rest of the

> registers are just that, D flipflop latches.

> 

> Then there will be the 2 to 1 (21) bit wide multiplexor to switch between video

> memory and program/data memory. The hardest part is keeping remebering that

> the 6809 latches data out of the CPU on the falling edge of the Qclk and latches

> data in to the CPU on the falling edge of the Eclk. Have to keep in mind when the

> data needs to  be presented to the CPU and when the CPU is passign data to

> external devices. After all that the first half of the Eclk cycle is doing display.

> 

> Mark, like I stated in the beginning, I got started with this to use the Coco as a

> postion controller and database for my telescopes. One thing that I wanted was to

> be able to drive an LCD panel of some type and have OS9 boot from a flash card or

> flash memory. I wanted at least 2 megs of sram and not dram. IDE interface and at

> least 4 mbytes of flash for storage.

> 

> Real pipe dreams was to add firewire or USB and a parallel port to control a CCD

> camera for astronomy.

> 

> So this will start as a home project and I have no idea of where it will go. I  have

> toyed with the thought of a FPGA version of the 6309 and run it at say around 15 to

> 25 MHz. These are future t hings to work on. I am right now having fun with it and

> learning VHDl in the same time frame. It is amazing what you can do with CPLDs

> and FPGAs. Some of the software development boards that I designed years ago

> would be more flexable and easier had I done a lot of the simple glue logic in these

> devices.

> 

> james

> 

> 

> On 6 Aug 2004 at 18:27, Mark Marlette wrote:

> 

> Date sent:              Fri, 06 Aug 2004 18:27:21 -0500

> To:                     CoCoList for Color Computer Enthusiasts

> <coco at maltedmedia.com>

> From:                   Mark Marlette <mmarlett at isd.net>

> Subject:                Re: [Coco] Re: Coco Repack

> 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>

> 

> > At 10:45 PM 8/6/2004 +0000, you wrote:

> >

> > The 63B09 = 2MHZ, 63C09=3MHZ and 63D09=4MHZ.

> >

> > James has quite a project just to do the GIME in a FPGA. Lets not

> > overwhelm the project and make it not happen. The paragraph below is a

> > HUGE task! Remember this is a hobby for most. To do the software,

> > hardware and test takes quite some time. Better yet how many people

> > would step forward and help out on it? How about put up the $$$ to buy

> > one????? I have over $5k out on the SuperBoard project, that doesn't

> > include my time. Love of the machine or stupidity...... :)

> >

> > It is quite a simple task to make the memory map for the GIME, it is

> > ALOT harder to perform all of the functions that is behind each bit.

> > The MMU is simple as well. Interrupt and timer functions are a bit

> > more complex and not documented the best. The video with all the

> > compatibility modes is something else as well. No doubt something to

> > be proud of, the GIME is the machine. I have been in direct contact

> > with the creators of this beast and it is AMAZING to me that nobody

> > has an internal document of it. I also do believe if they had it, I

> > would have it as our conversations went.

> >

> > Mark

> > Cloud-9

> >

> >

> > >IIIRC the 6309 is a 4 MHz part? I doubt it will run reliably after

> > >6-8 MHz. Even then, it could vary between chips. If you put a 6309 in

> > >FPGA you could drop some of the 6809 compatibility and possibly put

> > >in some new code, but then you'd lose program compatibility. Not sure

> > >how much that would affect NitrOS9 for the 6309 though. Still, if you

> > >do a CoCo repack with the joystick ports and replace the bit banger

> > >with USB (or two...), it would be a nice system. Wouldn't be 100%

> > >CoCo compatible once the ROMs were in place, but would be close.

> > >Would be very nice if the DECB ROM could be modified to use a USB

> > >floppy, and maybe HD. But DECB really doesn't need a HD for

> > >experimental purposes. Some sort of mass storage would be needed,

> > >maybe one of those USB "drives" would be easier to code in the ROM,

> > >but you'd have to transfer code from a PC to run DECB programs. The

> > >only reason I harp on DECB is the ease of programming for

> > >experiments. Basic09 is more powerful, it has similarities t

> > >  o Pascal, but CoCo BASIC is so darned easy to learn that for simple

> > >

> > > and/or quick experiments it would be preferred.

> > >

> > >

> > >--

> > >Frank Swygert

> > >Publisher, "American Independent

> > >Magazine" (AIM)

> > >*Elite* publication for those

> > >interested in all

> > >aspects of AMC

> > >history,performance,restoration,etc

> > >.

> > >(AMC,Rambler,Nash,Hudson,Jeep,etc.)

> > >http:farna.home.att.net/AIM.html

> > >(free download available!)

> > >

> > >

> > >

> > >-------------- Original message from coco-request at maltedmedia.com:

> > >--------------

> > >

> > > > Message: 3

> > > > Date: Fri, 06 Aug 2004 11:30:48 -0400

> > > > From: jdaggett at gate.net

> > > > Subject: Re: [Coco] Re: Coco Repack

> > > > To: CoCoList for Color Computer Enthusiasts

> > > > Message-ID: <41136BE8.14904.E66F7 at localhost>

> > > > Content-Type: text/plain; charset=US-ASCII

> > > >

> > > > Frank

> > > >

> > > > You are ringt if a FPGA version of the 6x09 were incorporated

> > > > along with an FPGA version of the GIME chip, breaking the 10 MHz

> > > > barrier will be no problem. Speed control can be done with

> > > > external clock ship. One by ICT can derive 1000's of frequencies

> > > > from a single crystal frequency. In fact the one chip that I was

> > > > looking at, from a 28.6868 MHz cyrstal I can derive over a 1000

> > > > different E and Q Clocks for the CPU from 400 KHz to 19 MHz.

> > > >

> > > > My initial intent was to use a 6309 and my new GIME chip and j ust

> > > > see how fast I can over clock the 6309. I have two bytes resevered

> > > > in the memory map to address the clock PLL chip.

> > > >

> > > > Just keep pushing the clock until the chip stops.

> > > >

> > > > james

> > >

> > >--

> > >Coco mailing list

> > >Coco at maltedmedia.com

> > >http://five.pairlist.net/mailman/listinfo/coco

> >

> >

> >

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