Caple C871i Manual de usuario descargar pdf (Pagina 234)

100

101

Apple II Computer Info

much faster than the standard ROM call.

I haven't looked at this code for a long time, and I'm sure there are ways to

improve it. Anyone, feel free to post possible enhancements!

;

; Read the joystick controls:

PRead anop

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sei

lda >$00C070 ; trigger paddles (6)

ldy #0 ; (3)

ldx #3 ; (3)

PRtime dex ; (2)

bne PRtime ; timing loop for 1st count (2,3)

PRead2 lda >$00C064 ; check paddle 0,1 status (6)

and #$8080 ; check high bits of each (3)

beq PRXit ; exit if both are done (2)

cmp #$0080 ; see if X only is active (3)

bmi PRBoth ; > no, do both (2,3)

beq PRXOnly ; > X axis only (2,3)

PRYonly iny ; (2)

bpl PRYmore ; (just for timing) (3)

bmi PRXit ; (prevent endless loop)

PRYmore bra PRead2 ; go back for more (3)

PRXOnly inx ; (2)

bmi PRXit ; (prevent endless loop) (2)

bra PRead2 ; go back for more (3)

PRBoth inx ; (2)

iny ; (2)

nop ; match timing of others (2)

bpl PRead2 ; (3)

PRXit plp

rts ; x = pdl(0), y = pdl(1)

;-------------------------------

Gary

* Nathan Mates http://www.ugcs.caltech.edu/~nathan/ *

* Ftp humor archiver: ftp to cco.caltech.edu, look in pub/humor *

* "Always listen to experts. They'll tell what can't be done, and *

* why. Then do it." -- Robert A. Heinlein, Lazarus Long *

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### joystick.read

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Apple II Computer Technical Information : Apple II Family Hardware Info

ftp://ground.ecn.uiowa.edu/2/apple2/miscinfo/hardware : May 2001 : 234 of 572

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Caple C871i Manual de usuario Pagina 234

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Caple C871i Manual de usuario Pagina 234

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