[Coco] Nitros9 L2 6809 DSK image?

[RETRO Innovations]

On 10/7/2017 2:43 PM, Barry Nelson wrote:
> So, did it boot?
> How much memory does it show?
> Type:
>
> mfree
>
>
I am happy to report that I successfully booted Nitros9 last night and 
mfree reports 1944K free :-)

I added the Barry Nelson 512kB Emulation functionality tonight (sorry, 
could not resist), but currently have to determine how to enable/disable 
it.  I initially put it on $ff91 bit 7, but at least Nitros9 resets that 
flag before booting to mem check, so it effectively turns it off :-)  I 
think I'll implement my "port knocking" approach for the emulation 
enable (like I did on CocoFLASH).

I assume 4MB works, and I have the NoCan support in, but I need a 
Nitros9 SDC image to try that will test it.

The issue at Tandy assembly was a stupid error:

if(flag_crm & cpu_address[12:4] == 12'hffe)

    data_bank = 9'hfe;

Should have been:

if(flag_crm & cpu_address[12:8] == 8'hfe)

    data_bank = 9'hfe;

Which I fixed last night, only to get an immediate screen corruption.  
On a hunch, I asked where OS9 screens are kept, and the answer was "top 
of memory".  My working firmware did not have the DISTO Video Bank code 
in place, and I watched Nitros9 try to store a $03 into $ff9b. Since my 
firmware didn't watch for that, Nitros 9 was putting the screen at 
2MB-8kB and I was pulling screen data from 512kB-8kB.  After 
implementing that register, all works.

Jim


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