Den Tue, 19 Jun 2018 09:35:02 +0100 skrev smf <smf@null.net>: > On 16/06/2018 20:34, Spiro Trikaliotis wrote: > > > What about JSR (two consecutive pushes), or an IRQ, NMI or BRK > > (three consecutive pushes)? > > Isn't that safe because the first write to the stack is followed by a > further write to the stack? Yeah, I haven't heard of any C64 expansions that put I/O in $100-$1FF. On some other 65xx board it might make sense though. Like use a 6532 and map 128 bytes of ram and I/O both in page 0 and 1, so the code can choose to use the ram as either stack or zero page ram as fit and for hardware simplification reasons the I/O might end up in both areas. But it would be hard to find any reason for using the stack pointer to write to I/O, especially using a jsr, irq, nmi or brk to do that. :) > What circumstance do you get a write followed where the next address > is going to be I/O? One single write can of course occur anywhere. -- (\_/) Copy the bunny to your mails to help (O.o) him achieve world domination. (> <) Come join the dark side. /_|_\ We have cookies.Received on 2018-06-20 02:00:06
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