Date   : Sun, 31 Mar 1996 03:33:32 +0100 (BST)
From   : Tom Seddon <T.W.Seddon@...>
Subject: More VIA queries

Hi,

I've just updated my VIA code so that timer reads return correct(ish) 
values -- although the timers themselves are updated only every 128 
cycles, on each read I add the number of cycles since the last update to 
the value.

But... how many cycles does the 6502 take when executing an instruction
before actually reading from memory? I suppose that really I should be
adding this value to the timer as well, in case the timer is incremented
between the start of the instruction and the time the memory read takes
place. Is this value constant for all instructions, or does it vary (in
which case I shan't bother!)? My ultimate aim is to get games which decode
themselves using the timers working, although I'll settle for greater
compatibility in general...

Thanks,

--Tom
 
    |     ** Tom Seddon **	  E-mail: T.W.Seddon@...
  - . -   			  www: http://www.ncl.ac.uk/~n5013784/
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