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Re: ZIP Chip Heartbreak
- Subject: Re: ZIP Chip Heartbreak
- From: dempson@atlantis.actrix.gen.nz (David Empson)
- Date: 1995/04/15
- Newsgroups: comp.sys.apple2
- Organization: Actrix Information Exchange
- References: <3mjgcd$qbn@netaxs.com> <3mn9ot$no1@news.blkbox.com> <3mo5m6$8a6@gap.cco.caltech.edu> <3mooi4$4o0@news.blkbox.com>
- Sender: news@actrix.gen.nz (News Administrator)
In article <3mooi4$4o0@news.blkbox.com>,
Glynne Tolar <gtolar@blkbox.com> wrote:
>
> Now I don't have the 6502 pinout in front of me but I seem to remember a
> DMA signal line to the CPU. Otherwise how would the CPU know to stop
> when a DMA cycle is occourring?
You're probably thinking of the RDY signal, which comes from the slots.
In a DMA cycle, the processor's clock input is stopped, and external
buffers are used to disconnect it from the address and data busses and
the R/W signal.
--
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand