[Coco] CoCo3 MMU Register question...

[Hugo Dufort]

This looks like an interesting and ambitious project!

The book "Assembly language programming for the Coco3" (1987) by 
Laurence Tepolt contains many reference diagrams that could help you 
figure out how the MMU works and how it is connected to the other 
components. You can find PDF copies of this book floating around the 
Web. A word of advice though: some informations in this book are 
imprecise or incomplete. You should complement the information in this 
book with other reference documents such as "Color Computer 1/2/3 
Hardware Programming" by Chris Lomont.

If I had a better understanding of hardware and enough time to start a 
new project, I'd try to create a music/sound coprocessor for the Coco2 & 
Coco3 using stock chips from the 8-bit era (e.g. the MOS 8580). There 
ought to be a way of wiring a sound chip directly to the board and 
communicate with it using a small range of memory addresses.

Hugo

Le 2015-03-30 14:53, Zippster a écrit :
> I have a scheme in mind, using a CPLD for address decoding, and high speed latches
> for the MMU bank registers, that would operate similarly to one set of CoCo3 MMU banks.
>
> With 8 banks (0-7), the same register locations in memory as the first instance in the CoCo3 (TR 0).
> Using each memory location ($FFA0 - $FFA7) to hold an 8-bit value for the memory block to map to (in a latch).
>
> Perhaps someone who knows about OS9 can tell me if a simplified MMU scheme like this would be
> suitable to compile OS9 to use.  This is without a second task register, and no ability to read the MMU registers.
> Those things could be implemented if necessary, but trying to keep it simple.
>
> Any thoughts or suggestions?  Unfortunately I don’t know squat about OS9’s memory usage.
>
> - Ed
>
>
>> On Mar 30, 2015, at 1:22 PM, Joe Grubbs <jsgrubbs at hotmail.com> wrote:
>>
>> I wish I could help because this sounds like a great project, but I don't know enough about my Coco3 to get this information.
>>
>>
>>
>> --- Original Message ---
>>
>> From: "Zippster" <zippster278 at gmail.com>
>> Sent: March 30, 2015 9:03 AM
>> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
>> Subject: [Coco] CoCo3 MMU Register question...
>>
>> Hi guys,
>>
>> Can anyone tell me what the default state (on power-up) is as far as the
>> values in the MMU registers in the CoCo3?
>>
>> Any information on how they are initialized/configured on startup would be appreciated.
>>
>> Working on a 2meg RAM upgrade for the CoCo2, and I want it to mimic CoCo3 RAM handling
>> as closely as possible.
>>
>> Thanks,
>>
>> - Ed
>


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