Caple C871i Bedienungsanleitung PDF herunterladen (Seite 220)

Apple II Computer Info

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### FILE : joystck.read

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### Created : Sunday, January 14, 1996 Modified: Sunday, January 14, 1996

### File Type: "TEXT" File Creator: "LMAN"

### File Size: 3757 bytes 3 KB

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Newsgroups: comp.sys.apple2

Path: news.weeg.uiowa.edu!news.uiowa.edu!hobbes.physics.uiowa.edu!zaphod.mps.ohio-

state.edu!cs.utexas.edu!sun-barr!ames!agate!dog.ee.lbl.gov!news!nosc!crash!pro-

nbs!pro-harold!pro-cajun!pro-gumbo!tgeer

(Smail3.1.28.1 #7) id m0nEz5Z-0000l2C; Thu, 21 Jan 93 02: 24 PST

From: [email protected] (System Administrator)

Subject: Re: Attention assembly programmers...

Organization: Apple Gumbo BBS

Date: Tue, 19 Jan 93 20:29:30 CST

Message-ID: <[email protected]>

In-Reply-To: [email protected] (Andre Prellwitz)

References: <[email protected]>

Lines: 59

In <[email protected]>

[email protected] (Andre Prellwitz) writes:

>A while ago someone posted about how to read the joystick on a //gs in native

>mode. They said that it was possible to read both paddles at once and there-

>fore get much more accurate readings. I don't recall exactly how to do this,

>but I've been trying the following: strobe the analog paddle reset ($c070)

>and then read locations $c064 and $c065 and wait until both return to zero.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Only the high bit of these locations is valid. When the high bit of either

location becomes 0 then the corresponding analog input has timed out. You

will actually get more accurate results by reading them one after the other

with the accumulator set to 8 bits wide and the index registers used to hold

the counts (16 bits wide). This allows for a much faster loop, giving better

resolution. Assuming that this routine is called from full native mode, the

following code will do the trick:

strobe equ $C070 ; analog input timing reset

pdl0 equ $C064 ; analog input 0

pdl1 equ $C065 ; analog input 1

start php ; save processor status register

phb ; and data bank register

sep #%100000 ; make accumulator 8 bits wide

lda #0 ; make data bank = 0

pha

plb

ldx #0 ; initialize the counters

txy

lda strobe ; strobe the timing reset

loop1 inx ; increment pdl0 count

lda pdl0 ; is high bit = 0?

bmi loop1 ; no, keep checking

lda strobe ; yes, strobe the timing reset again

Apple II Computer Technical Information : Apple II Family Hardware Info

ftp://ground.ecn.uiowa.edu/2/apple2/miscinfo/hardware : May 2001 : 220 of 572

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