Re: 65816 and I/O

From: MagerValp (MagerValp_at_cling.gu.se)
Date: 2001-01-20 01:55:54

>>>>> "j" == jbevren  <jbevren@starbase.globalpc.net> writes:

j> Since the machine starts from a game rom, I/O will be mapped in.
j> Once the SCPU gets permission to start, it locks DMA mode
j> permanently, with I/O enabled, and mirrors key locations to the c64
j> upon write, I.E. Dxxx, 0, 1.

j> The entire contents of RAM are also mirrored at an unknown (to me)
j> interval unless you select an optimisation mode, but that's beyond
j> our scope. ;)

RAM is mirrored at every write cycle if you don't enable optimisation.
I don't think it keeps the C64 in the game rom state though -- it's
possible to write to the memory underneat the I/O area. There's
certainly a lot of magic in the SCPU.

-- 
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