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Groups > comp.sys.apple2.programmer > #5402

Re: Sensing keypresses on the IIgs

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kegs@provalid.com (Kent Dickey) writes:

> Just do a long access instruction:
>
> 	LDA $E0C000
>
> which is the byte codes: AF 00 C0 E0.  No need to mess about with the bank
> register.  Use bank $E0 or $E1, since the I/O ports are always mapped in
> those banks.
>
> There's long indirect accesses as well.  You decide if you want the slight
> performance of using a 2-byte addresses with the DBR (and so changing the
> DBR a lot would negate the performance generally), or the convenience of
> long accesses.

Thanks for making this suggestion. I'm new to 65816 and I'm still
getting used to the new addressing modes. One thing that occurred to me
is that unless I set the accumulator to be 8 bits, then that LDA
instruction will actually read from $E0C000 and $E0C001. Based on the
documentation I've found that doesn't look like a big deal. Likewise
clearing the strobe by writing to $C010 would also write to $C011 -
correct?

Are these things I can just ignore? Thanks!

- James

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Thread

Sensing keypresses on the IIgs James Kruth <james@kruth.org> - 2020-02-01 16:11 -0500
  Re: Sensing keypresses on the IIgs jgandersen@gmail.com - 2020-02-01 14:17 -0800
    Re: Sensing keypresses on the IIgs James Kruth <james@kruth.org> - 2020-02-01 23:10 -0500
      Re: Sensing keypresses on the IIgs kegs@provalid.com (Kent Dickey) - 2020-02-01 23:17 -0600
        Re: Sensing keypresses on the IIgs James Kruth <james@kruth.org> - 2020-02-08 22:30 -0500
          Re: Sensing keypresses on the IIgs kegs@provalid.com (Kent Dickey) - 2020-02-09 15:26 -0600
  Re: Sensing keypresses on the IIgs Andy McFadden <thefadden@gmail.com> - 2020-02-02 07:52 -0800
    Re: Sensing keypresses on the IIgs James Kruth <james@kruth.org> - 2020-02-03 00:10 -0500
      Re: Sensing keypresses on the IIgs Andy McFadden <thefadden@gmail.com> - 2020-02-03 07:52 -0800
  Sensing keypresses on the IIgs gids.rs@sasktel.net - 2020-02-02 13:07 -0800
    Re: Sensing keypresses on the IIgs James Kruth <james@kruth.org> - 2020-02-02 23:57 -0500
      Re: Sensing keypresses on the IIgs gids.rs@sasktel.net - 2020-02-02 21:25 -0800
      Re: Sensing keypresses on the IIgs kelvin@pro-kegs.uucp (Kelvin Sherlock) - 2020-02-05 00:06 -0500
        Re: Sensing keypresses on the IIgs James Kruth <james@kruth.org> - 2020-02-08 22:56 -0500

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