Programmers
Kostya Shelonin, 1996
On some "secret" Command
INPUT / OUTPUT
we all loved CPU Z80.
Do not worry, it will not that
A register is the high byte address
port teams, ispolzyyuschih immediate operand, and ... execution
time commands IN / OUT. Many people are familiar skazhyt:
"What tyt mystery - he took, and looked at
reference ". But the thing is just a guide ...
Some time ago, it took me
write protsedypy, which used to synchronize the port # FF
(zakonchennyyu Test programmy, soderzhaschyyu ety protsedypy,
dymayu, you've nibyd yvidite and betaversiyu - tomorrow, if
zainteresyetes). So, it would have been nice if not one little
trouble - not converge the actual and estimated run time below
this fragment. This made me prizadymatsya ...
int IN A, (# FF)
INC A
INC BC
JP NZ, int
Estimated time - 31 bar
Real-time performance - 32 cycles
I looked in the directory data on komandy IN A, (n), takes 11
clock cycles, and command IN A, (C) in 12 cycles, and decided
instead of 11 cycles prikinyt 12 ... AND
estimated time to come together with the real!
This result is a bit puzzling, since
it's not a typo - in drygih references
also worth 11 clock cycles!
In connection with this "mystery", I
conducted a series of experiments on zamery runtime commands IN
and OUT, and here is a reward for the experiments:
n - 8-bit port address
r - register, 8 bits
team handbook really
IN A, (n) 11 cycles 12 cycles
IN r, (C) 12 cycles 12 cycles
OUT (n), A 11 clock cycles 12 cycles
OUT (C), r 12 cycles 12 cycles
Drygie I / O commands are not checked!
P.S. If you have any questions,
can contact me by phone:
(812) 151-44-43, Kostya
Or soap on oridzhin (2:5030 / 41.30).
With yvazheniem, K-Hacker from Omega group.
__________________________
