[Coco] CoCo 3 I/O map

[Gene Heskett]

On Tuesday 04 March 2014 00:55:26 William Astle did opine:

> A couple of notes for the GIME registers:
> 
> FF92 and FF93 also serve as interrupt status registers. Reading the
> register will have bits set for which interrupt source triggered the
> interrupt. Reading the register also resets the interrupt source state
> which means the state can only be detected on the first read after an
> interrupt occurs.
> 
> Otherwise, all registers in FF9x are write only. Reading them returns
> semi-random junk.
> 
> FFA0-FFBF are readable but only the lower six bits are valid when read.
> The upper two bits will contain semi-random junk.

We should qualify that William, the 2 meg kit from Tony does use all bits.  
I have one of those rare birds.
 
> Also, a note on the interrupt vectors (FFFx): On the coco1 and coco2,
> the contents of those vectors comes from the color basic ROM at BFFx. On
> the Coco3, however, the contents of those vectors comes from the top 16
> bytes of the 32K internal ROM (there is much information that states
> otherwise, but I have demonstrated this experimentally). In both cases,
> they are hard-mapped to ROM and cannot be changed regardless of any mode
> settings.
> 
> On 14-03-03 04:04 PM, Willard Goosey wrote:
> > Any additions?  Corrections?
> > 
> > 
> > 
> > 
> > --
> > Coco mailing list
> > Coco at maltedmedia.com
> > http://five.pairlist.net/mailman/listinfo/coco
> 
> --
> Coco mailing list
> Coco at maltedmedia.com
> http://five.pairlist.net/mailman/listinfo/coco


Cheers, Gene
-- 
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NOTICE: Will pay 100 USD for an HP-4815A defective but
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