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Example high-res assembly program

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Following is a program that I wrote that uses paddles 0 and 1 to define X
and Y coordinates for the end point of a line segment that begins in the
upper left corner of the screen. It uses Monitor routines PREAD and WAIT. It
uses some high-res Applesoft entry points too.

Here are these Applesoft entry points and their arguments:

1.) HGR - $F3E2
Clears the screen just like the BASIC command

2.) HGR2 - $F3D8
Just like the BASIC command; shows page 2 with no text at bottom

3.) HCOLOR - $F6F0
Takes a hi-res color, 0-7, in the X register

4.) HPLOT - $F457
Plots a single point. Also calls HPSON in advance.
A-reg = vert. coord
X-reg = horiz. coord, low-byte
Y-reg = horiz. coord, high-byte

5.) HLINE - $F53A
Draws a line anywhere on the screen, starting from the initial cursor
position, which can be altered with HPSON.
A-reg = horiz. coord, low-byte
X-reg = horiz. coord, high-byte
Y-reg = vert. coord

6.) HPOSN - $F411
This will set the initial cursor position.
The arguments re the same as HPLOT.


Just as a reminder, the high-res screen boundaries are 280 points
horizontal, by 192 vertical (with no text), or 160 vertical (with text).


Here is the Paddle Line program:

ORG $0300
JSR $F3E2 ; HGR
LDX #$03 ; HCOLOR 3
JSR $F6F0 ; SET HCOLOR
LDA #$00 ; INITIAL COORDS
TAX ; ALL ZERO
TAY ; ALL ZERO
JSR $F411 ; SET HPSON
LDX #$00 ; GET PADDLE 0 (HORIZ)
JSR $FB1E ; PREAD RETURNS IN Y-REG
TYA ; MOVE TO ACCUM
PHA ; SAVE ON STACK
JSR $FCA8 ; DELAY NECESSARY FOR PREAD
LDX #$01 ; GET PADDLE 1 (VERT)
JSR $FB1E ; PREAD
CPY #$A1 ; IS RESULT < 161?
BCC $0324 ; YES, SO SKIP NEXT
LDY #$A0  ; NO, SO LIMIT TO 160
LDX #$00 ; HORIZ. HIGH-BYTE ALWAYS ZERO
PLA ; GET SAVED HORIZ. LOW-BYTE FROM STACK
JSR $F53A ; HLINE
LDA #$FF ; LONG DELAY
JSR $FCA8 ; WAIT
JMP $0300 ; BEGIN AGAIN

I wrote this program using a pen and paper. My reference books were the
white Apple II manual and the Stanton arcade graphics book. I typed it in
and executed it on a platinum IIe with a b&w Apple composite monitor. It
worked the first time.

I have no idea what this program looks like on a color monitor, or with an
emulator.

Further Technical notes:

I wrote this program assuming that the subroutines would NOT preserve the
CPU registers. This may or may not be true in all cases, so it may be that
the program could be optimized.

It is necessary to let some amount of time pass between consecutive reads of
the paddles. The first delay is based on the initial paddle reading. If it's
0, then the delay may not be long enough, which could adversely affect the
reading of paddle 1. In most cases, this result is probably inconsequential.

-- 
]DF$
Apple II Book: http://macgui.com/newa2guide/
Usenet: http://macgui.com/usenet/  <-- get posts by email!
Apple II Web & Blog hosting: http://a2hq.com/

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Example high-res assembly program D Finnigan <dog_cow@macgui.com> - 2013-10-29 15:42 +0000
  Re: Example high-res assembly program Michael J. Mahon <mjmahon@aol.com> - 2013-10-29 13:08 -0500
    Re: Example high-res assembly program D Finnigan <dog_cow@macgui.com> - 2013-10-29 18:17 +0000
      Re: Example high-res assembly program Antoine Vignau <antoine.vignau@laposte.net> - 2013-10-29 11:27 -0700
      Re: Example high-res assembly program Michael J. Mahon <mjmahon@aol.com> - 2013-10-29 19:59 -0500
    Re: Example high-res assembly program aiiadict@gmail.com - 2013-10-29 13:51 -0700
      Re: Example high-res assembly program Antoine Vignau <antoine.vignau@laposte.net> - 2013-10-29 14:47 -0700
        Re: Example high-res assembly program aiiadict@gmail.com - 2013-10-30 10:02 -0700
          Re: Example high-res assembly program David Schmidt <schmidtd@my-deja.com> - 2013-10-30 13:10 -0400
            Re: Example high-res assembly program aiiadict@gmail.com - 2013-10-30 10:35 -0700
          Re: Example high-res assembly program Antoine Vignau <antoine.vignau@laposte.net> - 2013-10-31 11:13 -0700
            Re: Example high-res assembly program aiiadict@gmail.com - 2013-11-01 09:02 -0700
      Re: Example high-res assembly program aiiadict@gmail.com - 2013-10-31 09:49 -0700
        Re: Example high-res assembly program qkumba <peter.ferrie@gmail.com> - 2013-10-31 10:55 -0700
        Re: Example high-res assembly program aiiadict@gmail.com - 2013-11-01 10:52 -0700
          Re: Example high-res assembly program Michael J. Mahon <mjmahon@aol.com> - 2013-11-01 15:00 -0500
            Re: Example high-res assembly program aiiadict@gmail.com - 2013-11-02 09:48 -0700

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