6502 cycles and subtleties (was Re: Assembly on a Apple IIc+) - test-drb@ccmp.vtda.org

9 Feb 2003

On Feb 9, 10:55, Eric Smith wrote:
...
  > Are you sure?  My understanding is that PLP and
PLA increment the stack
...
   pointer
*before* fetching the byte off the stack.  [...]
 > Maybe you're thinking of PHP and PHA ([SP]:=A; SP:=SP+1), which take one
...
   cycle less
than PLP/PLA? 
 You're right, I was confused. 
Phew!  I was beginning to wonder if the 6502 is more bizarre than I
already knew :-)   You missed the mistake though -- I should have
written SP:=SP-1 (no it wasn't a test, I only just noticed).

-- 
Pete						Peter Turnbull
						Network Manager
						University of York