2018-03-26 01:53:41 +00:00
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\documentclass[twocolumn]{article}
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\usepackage{graphicx}
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2018-04-02 05:17:51 +00:00
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\usepackage{url}
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\usepackage{hyperref}
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2018-03-26 01:24:26 +00:00
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2018-03-26 01:53:41 +00:00
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\begin{document}
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2018-04-02 05:17:51 +00:00
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\title{Making an 8k Low-resolution Graphics Demo for the Apple II}
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2018-04-04 05:13:25 +00:00
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\author{by DEATER, AKA Vincent M. Weaver}
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2018-04-02 05:17:51 +00:00
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\date{}
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2018-03-26 01:53:41 +00:00
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\maketitle
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2018-03-26 01:24:26 +00:00
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2018-04-02 05:17:51 +00:00
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\section{Why would anyone do this?}
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2018-04-04 05:13:25 +00:00
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While making an inside-joke filled game for my retro system of choice,
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the Apple II, I needed to create a Final-Fantasy-esque
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flying-over-the-planet sequence.
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I was originally going to fake this, but then I found that it was just barely
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2018-04-02 05:17:51 +00:00
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possible to achieve this in real time.
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2018-04-04 05:13:25 +00:00
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Once I got the code working I realized it would be great as part of a
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2018-04-02 05:17:51 +00:00
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graphics demo, so off on that tangent I went.
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2018-04-04 05:13:25 +00:00
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This went well, despite the fact that all I know about the demoscene I learned
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from a few viewings of the Future Crew {\em Second Reality} demo mixed with
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dimly remembered Commodore 64 and Amiga flamewars.
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2018-04-02 05:17:51 +00:00
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2018-04-04 05:13:25 +00:00
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% from a few decades ago.
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2018-04-02 05:17:51 +00:00
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% This started out as some SNES style mode7 pseudo-3d graphics code
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% I came up with while working on my TF7 game. The graphics looked
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% pretty cool, so I started developing a demo around it.
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2018-04-04 05:13:25 +00:00
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%To make thins even better, the code ended up being roughly around 8kB so a
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%lot of time was wasted fitting it under that arbitrary size limitation.
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2018-04-02 05:17:51 +00:00
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2018-04-04 05:13:25 +00:00
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While I hope you enjoy the description of the demo and the work that
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went into it, I do suspect the whole enterprise is only of note
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because so few people write demos for the Apple II platform.
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%So in the end this ends up being impressive mostly because so few people
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%have bothered to write demos for this particular platform.
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I would like to make a shout out to the FrenchTouch group whose Apple II
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2018-04-02 05:17:51 +00:00
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demos put this one to shame.
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% The codesize ended up being roughly around 8kB, so I thought I'd
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% make it into an 8k demo. There aren't many out there for the Apple II.
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% and a Mockingboard sound card.
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% The demo tries to hit the lowest common denominator for Apple II systems,
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% so in theory you could have run this on an Apple II in 1977 if you
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% were rich enough to afford 48k of RAM. The Mockingboard sound wasn't
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% available until 1981, but still this all predates the Commodore 64.
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%I was writing a game for the Apple II and realized I had come up with
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%some clever Super-Nintendo (SNES) style graphics routines that were just
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%crying to be turned into a demo-scene style demo.
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%The Apple II was the first computer I had access too, and I grew up in an odd
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%neighborhood where it was all Apples and not a Commodore to be seen.
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%My family long ago got rid of our machine, but I rescued an Apple IIe platinum
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%from the dumpster one day and have dragged it from state to state ever since.
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%I find 6502 assembly to be oddly therapeutic, and will code in it when other
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%projects become too stressful. Especially when Linux up and hangs on me
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%because firefox tried to do something stupid in javascript. I then pine for
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%the days when you could do something useful in 64k of RAM, and not have your
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%machine fall over because somehow 4GB is not enough.
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%Background:
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%The Apple II was the first computer I programmed on, lo many years ago.
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%Mostly in Applesoft BASIC (which ended up being the only Microsoft product
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%I ever liked) but I was starting to get into assembly language about the
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%time my family got a 386 system.
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%I've revisited over the years, with some 6502 programming to show I could.
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%My skills were not that great, I had one of my size-optimization projects
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%crowd re-optimized. For a while I had a side-gig re-optimizing modern games
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%in BASIC, before getting sidetracked into going full in on 6502 assembly
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%again.
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%Introduced in 1977.
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%The Apple II runs at 1.XX check Megahertz. 6502, which can easily
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%address 64 kB of RAM (more with bank switching). Shipped with as little
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%as 4kB of RAM. Three registers, (A,X,Y) but a large ``zero page'' which
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%gives you register-like actions on the first 256 bytes of RAM.
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%
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%DOS3.3 operating system with 140k floppies. Amazing programming by Wozniak,
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%allowing all kinds of floppy protection shenanigans (cite 4am, previous
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%article).
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\section{The Hardware}
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2018-04-04 05:13:25 +00:00
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The Apple II was introduced in 1977.
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This demo should run on an original system, though I do not
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have hardware quite that old to test on.
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I like to troll C64 fans by noting this predates the Commodore 64 by
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five years.
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\vspace{1ex}
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\noindent
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{\bf CPU, RAM and Storage:}
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The Apple II has a 6502 processor running at roughly 1.023MHz.
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Early models only shipped with 4k of RAM, but later 48k, 64k, and 128k
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systems were common.
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While the demo itself fits in 8k, it decompresses to a larger size and uses
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a full 48k of RAM;
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this would have been very expensive in 1977.
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Also in 1977 you would probably be loading this from cassette tape.
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It would be another year before Woz's single-sided
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$5\frac{1}{4}$" Disk II came about (eventually offering 140k of
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storage per side with the release of Apple DOS3.3 in 1980).
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\vspace{1ex}
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\noindent
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{\bf Sound:}
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The only sound available in a stock Apple II is a bit-banged speaker.
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There was no timer interrupt; if you wanted music you had to cycle-count
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via the CPU to get the waveforms you needed.
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The demo uses a Mockingboard soundcard which was introduced in 1981.
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This board contains dual AY-3-8910 sound generation chips connected via
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6522 I/O chips.
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Each sound chip provides 3 channels of square waves as well as noise and
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envelope effects.
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\vspace{1ex}
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\noindent
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{\bf Graphics:}
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It is hard to imagine now, but the Apple II had nice graphics for its time.
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Compared to later competitors, however, it had some limitations.
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\begin{center}
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\begin{tabular}{|c|c|}
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\hline
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Hardware Sprites & No \\
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User-defined charset & No \\
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Blanking interrupts & No \\
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Palette selection & No \\
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Linear framebuffer & No \\
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Hardware scrolling & No \\
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Hardware page flip & Yes \\
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\hline
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\end{tabular}
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\end{center}
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The hi-res graphics mode was a complex mess of NTSC hacks by Woz.
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You got approximately 280x192 resolution, with 6 colors available.
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However the colors were from NTSC artifacts and there were limitations
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on which colors could be next to each other (in blocks of 3.5 pixels).
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There was plenty of fringing on edges, and colors changed depending on
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whether they were drawn at odd or even pixels.
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To add to the madness, the framebuffer is interleaved in a complex way,
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and pixels are drawn least-significant-bit first (all of this to make
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DRAM refresh better and to shave a few 7400 series logic chips from the design).
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You do get two pages of graphics, Page 1 is at
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\$2000\footnote{On 6502 systems hexadecimal values are
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indicated by the dollar sign}
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and Page 2 at \$4000.
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Optionally 4 lines of text can be shown at the bottom of the
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screen instead of graphics.
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The lo-res mode is a bit easier to use.
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It provides 40x48 blocks (40x40 if the four
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lines of text are displayed at the bottom).
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Fifteen colors are available (there are two greys which are indistinguishable).
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Again the addresses are interleaved. Lo-res Page 1 is at \$400
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and Page 2 is at \$800.
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Some amazing effects can be achieved by cycle counting, reading
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the floating bus, and racing the beam while toggling graphics
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modes on the fly.
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Unfortunately for you this demo does not do any of those things
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so you will not be reading about that today.
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2018-04-02 05:17:51 +00:00
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%Later models added double low-res (80x48) and double hi-res (x y in
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%NTSC 15 color) but didn't appear until 198x, and only on later IIe, IIc
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%models.
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%Apple also came out with the IIgs which arguably was much more advanced
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%and cheaper than the Mac, but Apple cancelled the II line much to the
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%sadness of the users (Apple II forever).
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2018-04-04 05:13:25 +00:00
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\section{Development Setup}
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2018-03-26 01:24:26 +00:00
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2018-04-04 05:13:25 +00:00
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I do all of my coding under Linux, using the nano text editor.
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I use the ca65 assembler from the cc65 project, which I find to be a reasonable
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tool although many ``real'' Apple II programmers look down on it for some
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reason.
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2018-04-04 05:13:25 +00:00
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I cross-compile the code, construct Apple DOS3.3 disk images using
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custom tools I have written, and then do most testing in an emulator.
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AppleWin (run under the wine emulator) is the easiest to use, but
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MESS/MAME has cleaner sound.
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2018-04-04 05:13:25 +00:00
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Once the code appears to work, I put it on a USB stick and transfer
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to actual hardware using a CFFA3000 disk emulator installed in
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the actual Apple II (an Apple IIe platinum edition).
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2018-03-26 01:24:26 +00:00
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2018-04-02 05:17:51 +00:00
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%\section{Related Work}
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%
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%See anything by the group FrenchTouch, whose Apple II demos outclass
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%mine by a lot.
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% http://www.deater.net/weave/vmwprod/mode7_demo/
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\section{The Demo}
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\subsection{BOOTLOADER}
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2018-04-04 05:13:25 +00:00
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An Applesoft BASIC ``HELLO'' program loads the binary automatically at bootup.
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This does not count towards the executable size, as you could manually BRUN
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the 8k program if you wanted.
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2018-04-02 05:17:51 +00:00
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2018-04-04 05:13:25 +00:00
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To make the loading time slightly more interesting the binary is loaded at
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address \$2000 (hi-res page1) and BASIC is nice enough to enable
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graphics mode first so you can watch the display get filled with the random
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pattern of the compressed image.
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This entirely fills the 8k of the display, or would
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if we POKEd the right address to turn off
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the 4 lines of text on the bottom of the screen.
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2018-04-04 05:13:25 +00:00
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Upon loading, execution starts at address \$2000
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\subsection{DECOMPRESSER}
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2018-04-04 05:13:25 +00:00
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\begin{figure}[tb]
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\begin{center}
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\includegraphics[width=2in]{figures/hidden_vmw.png}
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\end{center}
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\caption{VMW logo hidden in the executable data.\label{fig:vmw}}
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\end{figure}
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2018-04-02 05:17:51 +00:00
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2018-04-04 05:13:25 +00:00
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The binary is encoded with the LZ4 algorithm.
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We flip to hi-res Page 2 and decompress there so the user continues to get
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a show of random noise.
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The 6502 size-optimized LZ4 decompression code was written by qkumba
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(Peter Ferrie).
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% http://pferrie.host22.com/misc/appleii.htm
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The program and data decompress to around 22k starting at \$4000.
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It over-writes parts of DOS3.3, but since we will not be using the disk
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any more this is not an issue.
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If you look carefully at the upper left corner of the screen during
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decompress you will see my triangular logo, which is supposed to evoke
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my VMW initials (see Figure~\ref{fig:vmw}).
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To do this I had to put the proper bit pattern at the interleaved
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addresses of \$4000, \$4400, \$4800, and \$4C00.
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This turned out to be way more trouble than it was worth.
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As an interesting note, the image data at \$4000 is executed as it maps
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to (mostly) harmless code.
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The demo was optimized to fit in 8k, and this is difficult when your program
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is compressed.
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Removing instructions sometimes makes the binary {\em larger} as it no longer
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compresses as well.
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Long runs of values (such as 0 padding) are essentially free.
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This mostly turned into an exercise of guess-and-check until everything fit.
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\subsection{FADE EFFECT}
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2018-04-04 05:13:25 +00:00
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The title screen fades in from black.
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2018-04-04 05:13:25 +00:00
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This is a software hack as the Apple II does not have palette support.
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The image is loaded to an off-screen buffer and a lookup table is used to
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copy in the faded versions on the fly.
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\subsection{TITLE SCREEN}
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2018-04-04 05:13:25 +00:00
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\begin{figure}[tb]
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\begin{center}
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\includegraphics[width=\columnwidth]{figures/mode7_demo_title.png}
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\end{center}
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\caption{The title screen.\label{fig:title}}
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\end{figure}
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2018-04-04 05:13:25 +00:00
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Once decompression is done, execution continues at address \$4000.
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We switch to low-res mode for the rest of the demo.
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A title screen is loaded, as seen in Figure~\ref{fig:title}.
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The image is run-length encoded (RLE) which is
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probably unnecessary when being further LZ4 encoded.
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(The LZ4 compression was a late addition to this endeavor).
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Why not save some space and just load our demo at \$400 and negate the need
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to copy the image in place?
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Remember the graphics are 40x48 (shared with the text display region).
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It might be easier to think of it as 40x24 characters, with the top / bottom
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4-bits of each ASCII character being interpreted as colors for a half-height
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block.
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If you do the math you will find this takes 960 bytes of space, but the memory
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map reserves 1k for this mode.
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There are ``holes'' in the address range that are not displayed, and
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various pieces of hardware can use these as scratchpad memory.
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This means just overwriting the whole 1k with data might not work out well
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unless you know what you are doing.
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To this end the RLE decompression code skips the holes just to be safe.
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The title screen has scrolling text at the bottom.
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This is nothing fancy, the text is in a buffer off screen and a 40x4
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chunk of RAM is copied in every so many cycles.
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You might notice that there is tearing/jitter in the scrolling even
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though we are double-buffering the graphics.
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Sadly there is not a reliable cross-platform way to get the VBLANK info
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on Apple II machines, especially the older models.
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This is even more noticeable in the recorded video, as the capture card and
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movie encoding conspire to make this look worse than things look in person.
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2018-04-02 05:17:51 +00:00
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\subsection{MOCKINGBOARD MUSIC}
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2018-04-04 05:13:25 +00:00
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No demo is complete without some exciting background music.
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I like chiptune music, especially the kind you can find that is made
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for AY-3-8910 based systems.
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I gained some expertise during the long wait for my Mockingboard to arrive
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by building a Raspberry Pi chiptune player that is essentially the same
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hardware.
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The song being played is a stripped down and re-arranged version of
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``Electric Wave'' from CC'00 by EA (Ilya Abrosimov).
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Most of my sound infrastructure involves YM5 files, a format commonly
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used by ZX Spectrum and ATARI ST users.
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These are essentially just AY-3-8910 register dumps taken at 50Hz.
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To play these back just set up the sound card to interrupt 50 times a second
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and then write out the 14 register values from that frame.
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% To program the Mockingboard, each AY-3-8910 chip has 14 sound related
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% registers that control the 3 channels. Each AY chip has a dedicated
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% VIA 6522 parallel I/O chip that handles the I/O.
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Writing out the registers quickly enough is a challenge on the Apple II.
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For each register you have to do a handshake then set both the register
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number and the value.
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It is hard to do this in less than forty 1MHz cycles for each register.
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With complex chiptune files (especially those written on an ST with much
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faster hardware) it is sometimes not possible to get exact playback
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due to the delay.
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Further slowdown happens as you want to write both AY chips (the output
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is stereo, with one AY on the left and one on the right).
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% I have a whole suite of code for manipulating YM sound data, in my
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% vmw-meter git repository.
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Our code detects a Mockingboard at startup, we are lazy and only support
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finding the card in Slot 4 (which is a fairly typically location).
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% The first step for getting this to work is detecting if a Mockingboard is
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%% there. This can be in any slot 1-7 on the Apple II, though typically
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% Slot 4 is standard (in this demo we only check slot 4).
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The board is initialized, and then one of the 6522 timers is set to
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interrupt at 25Hz.
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% (it has to be an on-board timer as the default
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% Apple II has no timers).
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Why 25Hz and not 50Hz? At 50Hz with 14 registers you use 700 bytes/s.
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So a 2 minute song would take 84k of RAM, much more than is available.
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To allow the song to fit in memory (without the fancy circular buffer
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decompression utilized in my Chiptune Player Music Disk demo) we have
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to reduce the size significantly.
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First we reduce the music to only need to be updated at 25Hz.
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We reduce the register data from 14 bytes to 11 bytes by stripping off
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the envelope effects and packing together some of the fields that have
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unused bits.
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To help with latency on playback we keep track of the last frame written
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and only write to the registers that have changed.
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In the end the sound quality suffered a bit, but we were able to fit an
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acceptably catchy chiptune inside of our 8k payload.
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2018-04-02 05:17:51 +00:00
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\subsection{MODE7 BACKGROUND}
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2018-04-04 05:13:25 +00:00
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``MODE7'' is a Super Nintendo (SNES) graphics mode that took a tiled
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2018-04-02 05:17:51 +00:00
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background and transformed it to look as if it was squashed out to
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the horizon, giving a 3d look. The SNES did this in hardware, but
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in this demo we do this in software.
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As found on Wikipedia, the transform is of the type
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[x'] = [a b]([x]-[x0])+[x0]
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[y'] [c d]([y] [y0]) [y0]
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For our code, we managed to reduce things to a small number of additions
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and subtractions for each pixel on the screen. Of course the 6502 can't
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do floating point, so we do fixed point math. We convert as much as we
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can to table lookups that are pre-calculated. We also make liberal use
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of self-modifying code.
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Despite all of this there are still some cases where we have to do a
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16bit x 16bit = 32bit multiply, something that is *really* slow on 6502,
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around 700 cycles (for a 8.8 x 8.8 fixed point multiply).
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To make this faster we use a method described by Stephen Judd.
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The key to note is that $(a+b)^{2} = a^{2}+2ab+b^{2}$
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and $(a-b)^{2}=a^{2}-2ab+b^{2}$
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and if you add them you can simplify to:
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$a\times b =\frac{(a+b)^{2}}{4} - \frac{(a-b)^2}{4}$
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This is you have a table of squares from 0..511 (all 8-bit a+b and a-b
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will fall in this range) then you can convert a multiply into a table
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lookup plus a subtract.
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The downsize is you will need 2kB of squares lookup tables (which can
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be generated at startup). This reduces the multiply cost to the order
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of 200 to 250 cycles.
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By using the fast multiply and a lot of careful optimization you can
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generate a Mode7 background in 40x40 graphics mode at about 5 frames/second.
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The engine can be parameterized with different tilesets to use, which we
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do to provide both a black+white checkerboard background, as well as the
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island background from the TFV game.
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\subsection{BOUNCING BALL ON CHECKERBOARD}
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|
2018-04-04 05:13:25 +00:00
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\begin{figure}
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\begin{center}
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\includegraphics[width=\columnwidth]{figures/m7_screen1.jpg}
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\caption{Bouncing ball on infinite checkerboard.\label{fig:ball}}
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\end{center}
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\end{figure}
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|
2018-04-02 05:17:51 +00:00
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What would a demo be without some sort of bouncing geometric shape.
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This is just done with 16 sprites. The sphere was modeled in OpenGL
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from a 2000-era game-engine that I never finished. I then took screenshots
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and then reduced the size/color to an appropriate value.
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The shadow is also just sprites.
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The clicking noise on bounce is just touching the speaker at \$C030.
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It's mostly there to give some sound effects for those playing the demo
|
2018-04-04 05:13:25 +00:00
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without a Mockingboard.
|
2018-03-26 01:24:26 +00:00
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2018-04-02 05:17:51 +00:00
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\subsection{TFV SPACESHIP FLYING}
|
2018-03-26 01:24:26 +00:00
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|
2018-04-04 05:13:25 +00:00
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|
\begin{figure}[tb]
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|
\begin{center}
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|
\includegraphics[width=\columnwidth]{figures/m7_screen4.jpg}
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\end{center}
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|
\caption{Spaceship flying over an island.\label{fig:tb1}}
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|
\end{figure}
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|
2018-04-02 05:17:51 +00:00
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|
The spaceship, water splash, and shadows are all sprites. This is all
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|
done in software, the Apple II has no sprite hardware.
|
2018-03-26 01:24:26 +00:00
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|
2018-04-02 05:17:51 +00:00
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This is the TFV game engine flying-spaceship code, with the keyboard
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|
routines replaced to read from memory instead (sort of like a script
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|
|
of what to do when).
|
2018-03-26 01:24:26 +00:00
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|
2018-04-02 05:17:51 +00:00
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|
\subsection{STARFIELD}
|
2018-03-26 01:24:26 +00:00
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|
2018-04-04 05:13:25 +00:00
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|
\begin{figure}[tb]
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|
|
\begin{center}
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|
|
\includegraphics[width=\columnwidth]{figures/m7_screen3.jpg}
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|
\end{center}
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|
\caption{Spaceship with starfield.\label{fig:stars}}
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|
\end{figure}
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|
2018-04-02 05:17:51 +00:00
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|
The starfield is your typical starfield code. Only 16 stars are modeled.
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|
It re-uses the fast-multiply code from the mode7 graphics.
|
2018-03-26 01:24:26 +00:00
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|
2018-04-02 05:17:51 +00:00
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|
Random number generation is not fast on the 6502, so we cheat.
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|
|
Originally we had a 256-byte blob of "random" values generated earlier.
|
2018-03-26 01:24:26 +00:00
|
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|
2018-04-02 05:17:51 +00:00
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|
This wasted space, so now instead we just treat the executable code
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|
|
at \$5000 as if it were a block of random numbers. This was arbitrarily
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|
|
chosen, I tried different areas of memory until I got one where the
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|
|
stars seemed to move in a pleasing pattern.
|
2018-03-26 01:24:26 +00:00
|
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|
2018-04-02 05:17:51 +00:00
|
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|
A simple state machine controls if the stars move or not, whether the
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|
|
background is cleared or not (the streak effect) and what color the
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|
|
background is (for the blue flash).
|
2018-03-26 01:24:26 +00:00
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|
2018-04-02 05:17:51 +00:00
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|
The ship moving to the distance is just done with different sized sprites.
|
2018-03-26 01:24:26 +00:00
|
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|
2018-04-02 05:17:51 +00:00
|
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|
\subsection{RASTERBARS/CREDITS}
|
2018-03-26 01:24:26 +00:00
|
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|
|
2018-04-04 05:13:25 +00:00
|
|
|
\begin{figure}[tb]
|
|
|
|
\begin{center}
|
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|
|
\includegraphics[width=\columnwidth]{figures/m7_screen2.jpg}
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|
|
\end{center}
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|
|
\caption{Rasterbars, stars, and credits.\label{fig:credits}}
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|
|
\end{figure}
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|
2018-04-02 05:17:51 +00:00
|
|
|
The credits happen with the starfield continuing to run.
|
2018-03-26 01:24:26 +00:00
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|
2018-04-02 05:17:51 +00:00
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|
The text is written in the bottom 4 lines of the screen. Some inverse-mode
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|
|
space characters are used to try to make it look like graphics are surrounding
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|
|
the text. It's actually possible with careful cycle counting to switch
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|
|
modes fast enough to have actual mixed graphics/text (See the FrenchTouch
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|
|
|
demos) but I was too lazy to attempt that here.
|
2018-03-26 01:24:26 +00:00
|
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|
2018-04-02 05:17:51 +00:00
|
|
|
The rasterbar effect isn't really rasterbars, it's just a rainbow assortment
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|
|
of lines being drawn with a SINEWAVE lookup table.
|
2018-03-26 01:24:26 +00:00
|
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|
|
2018-04-02 05:17:51 +00:00
|
|
|
It's the same rasterbar code from my chiptune player demo. I ended up
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|
|
optimizing it a lot via inlining and a few other ways because it turned
|
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|
|
out just drawing a horizontal line can take a very long time.
|
2018-03-26 01:24:26 +00:00
|
|
|
|
2018-04-02 05:17:51 +00:00
|
|
|
The rotating text is just taking the output string and rapidly rotating the
|
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|
|
character values through the ASCII table.
|
2018-03-26 01:24:26 +00:00
|
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|
|
2018-04-02 05:17:51 +00:00
|
|
|
The annoying clicking noise is the same speaker effect caused by hitting
|
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|
|
\$C030.
|
2018-03-26 01:24:26 +00:00
|
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|
|
2018-04-02 05:17:51 +00:00
|
|
|
Choosing who to thank ended up being extremely critical to fitting in 8kB,
|
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|
|
as unique text strings do not compress well. I'm also still not satisfied
|
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|
|
with how the centering looks.
|
2018-03-26 01:24:26 +00:00
|
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|
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|
|
2018-04-02 05:17:51 +00:00
|
|
|
More details, disk image, and full source can be found at the website:
|
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|
|
\url{http://www.deater.net/weave/vmwprod/mode7_demo/}
|
2018-03-26 01:24:26 +00:00
|
|
|
|
2018-04-02 05:17:51 +00:00
|
|
|
\begin{table}
|
2018-04-04 05:13:25 +00:00
|
|
|
\begin{center}
|
2018-04-02 05:17:51 +00:00
|
|
|
\begin{verbatim}
|
2018-03-26 01:24:26 +00:00
|
|
|
|
2018-04-04 05:13:25 +00:00
|
|
|
------------- $ffff
|
|
|
|
| ROM/IO |
|
|
|
|
------------- $c000
|
|
|
|
| |
|
|
|
|
| Uncompressed|
|
|
|
|
| Code/Data |
|
|
|
|
| |
|
|
|
|
------------- $4000
|
|
|
|
| Compressed |
|
|
|
|
| Code |
|
|
|
|
------------- $2000
|
|
|
|
| free |
|
|
|
|
------------- $1c00
|
|
|
|
| Scroll |
|
|
|
|
| Data |
|
|
|
|
------------- $1800
|
|
|
|
| Multiply |
|
|
|
|
| Tables |
|
|
|
|
------------- $1000
|
|
|
|
| LORES pg 3 |
|
|
|
|
------------- $0c00
|
|
|
|
| LORES pg 2 |
|
|
|
|
------------- $0800
|
|
|
|
| LORES pg 1 |
|
|
|
|
------------- $0400
|
|
|
|
|free/vectors |
|
|
|
|
------------- $0200
|
|
|
|
| stack |
|
|
|
|
------------- $0100
|
|
|
|
| zero pg |
|
|
|
|
------------- $0000
|
2018-03-26 01:24:26 +00:00
|
|
|
|
2018-04-02 05:17:51 +00:00
|
|
|
\end{verbatim}
|
2018-04-04 05:13:25 +00:00
|
|
|
\end{center}
|
2018-04-02 05:17:51 +00:00
|
|
|
\caption{Memory Map (not to scale)}
|
|
|
|
\end{table}
|
2018-03-26 01:24:26 +00:00
|
|
|
|
2018-03-26 01:53:41 +00:00
|
|
|
\end{document}
|