[Coco] Doubt about how 68xx interrupt vectors work

Darren A mechacoco at gmail.com
Sat Jul 21 21:46:06 EDT 2012

On Sat, Jul 21, 2012 at 6:23 PM, Juan Castro wrote:
> Ahhh, thanks. I wonder, if an expansion ROM is present, will the new
> contents appear at these last addresses, or the previous ones? I would
> imagine you could put new addresses and they would be active.

The SAM chip in the CoCo 1/2 and the GIME in the CoCo 3 always produce
a device select code for the internal ROM when FFE0-FFFF is accessed.
To have the vectors come from an external ROM, you would need to
decode the address range externally, assert the SLENB* signal and
produce the ROM chip select yourself.


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