[Coco] Nitros9 L3

[Bill Nobel]

Oh, your right….  I forgot about the 6309 trap vectors.  But I see that in Nitros9 module 3 values are stored.  $10ff @ $0000, $0008 @ $0002 & $20fe @ $0004 not sure as to the reason yet.

Bill Nobel

> On Nov 3, 2014, at 9:24 AM, Robert Gault <robert.gault at att.net> wrote:
> 
> Bill Nobel wrote:
>> Yes, I saw those defs, but I notice in my disarm of Nitros9 module that it
> > uses System DP starting at $0000 which was def’d in level 2 as FHL/Isted
> > WD1002-05 base address.  It is used now as pointers to I'm assuming
> > SCF/RBF base addresses.
>> 
>> <snip>
>> Bill Nobel
>> 
> 
> Bill,
> 
> All the source code I've seen for Level3 assumes a 6309. The 6309 requires a trap for illegal coding and uses the address at $FFF0 to jump to the code. Tandy never used that (6809 only) so the ROM at $FFF0 reads $0000.
> Given the above, a 6309 requires some code at $0000 to at least jump to the actual trap routine.
> 
> You could try leaving out any trap code but that would be risky. Sooner or later something will go wrong and vector to $0000 assuming there is valid code at that location.
> 
> Robert
> 
> 
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