On 8/6/2012 3:12 PM, Steven Hirsch wrote:
Boisy is most definitely the right person to ask about the intricacies of OS-9/NitrOS-9 and 6809/6309 assembly programming. He's forgotten more about it than I'll ever hope to know. I'd love to see a minimum of 512k on such a card, and it goes without saying that I want one :-).
I agree, the same way as my PCPI clone takes either 128K or 512K chips.One question is how to implement the memory management. There seems to be a standard in the 6809 world where the space at $FF00 (?) contains 16 write-only registers that map logical 4K blocks to arbitrary physical memory. That would require a lot more resources to implement than is available in simple CPLDs easy to hand solder. Another extreme is a single 32K block mappable to physical RAM. I wonder what is the minimum for OS9 level 2? I guess reading the CoCo 3 manual may help.
-Alex.