Category Archives: CoCo Programming

CoCo 3 – Game Collision Detection Routine (6809 assembly)

Posted on January 29, 2024 by nowhereman999

I’ve been recently toying with the idea of writing a game using the CoCo 3 256 x 200 x 16 colour resolution and I got far enough along to require collision detection of the game sprites. I wrote my own code … Continue reading →

Posted in CoCo Programming | Tagged , , , , , , , , | 2 Comments

MOS 6502 to Motorola 6809 Assembly Language Transcoding

Posted on February 15, 2023 by nowhereman999

I’ve started looking at some MOS 6502 assembly code and I’m in the process of transcoding it to Motorola 6809 assembly. I’ve found an excellent PDF online describing the process of translating programs from the 6502 to the 6809 starting … Continue reading →

Posted in CoCo Programming | 7 Comments

Found some copy protection code in Joust

Posted on June 23, 2021 by nowhereman999

There is some tricky copy protection used in Joust to stop anyone tampering with the code. I just wanted to document it here just in case anyone wants to learn about it. I was playing around with the Joust code … Continue reading →

Posted in CoCo Programming, Emulation | 7 Comments

Defender Conversion for the CoCo 3 – Part 6 – Three out of Three attract Screens are converted

Posted on February 8, 2018 by nowhereman999

Today I completed converting the Defender Arcade code to play through all three attract modes.  The last one was definitely the hardest as it contains the sprites moving around the screen.  I also had to convert how Defender draws the … Continue reading →

Posted in CoCo Programming | Tagged , , , , | 9 Comments

Defender Conversion for the CoCo 3 – Part 5 – Another cool 6809 coding trick they used

Posted on January 28, 2018 by nowhereman999

Hello, I just wanted to document this neat little trick here.  For changing the colour of one of the 16 stars on screen randomly in Defender they do the following: * Table of stars @ $AF9D to $AFDC * Format … Continue reading →

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Defender Conversion for the CoCo 3 – Part 4 – Two out of Three Attract Screens are converted

Posted on January 25, 2018 by nowhereman999

I’ve been working hard on the Defender conversion and am happy with the progress and how well things are going.  I uploaded a video on YouTube showing that I now have two out of three attract screens working.  The code … Continue reading →

Posted in CoCo Programming, Emulation | Tagged , , , , , , , | 3 Comments

Arcade Machine Conversion to the CoCo Overview

Posted on January 20, 2018 by nowhereman999

Hello, in a recent post I got a comment from username Perezernestoj who asked if I could convert Super Pac Man as my next game for the CoCo after I complete Defender.  I explained how much work this is and … Continue reading →

Posted in CoCo Programming | 1 Comment

Defender Conversion for the CoCo 3 – Part 3 – Two more 6809 coding tricks they used

Posted on January 14, 2018 by nowhereman999

Below are a couple of coding tricks I’ve learned from Defender this week.  I thought I’d pass along the tricks for others to use, if they aren’t already. For simple loop counting, a nice fast way is to load an … Continue reading →

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Defender Conversion for the CoCo 3 – Part 2 – Short and Sweet

Posted on January 6, 2018 by nowhereman999

Just a little blog entry to share a neat little bit of 6809 code. I’m really impressed with how well the 6809 is programmed in Defender.  I was decoding some of the Defender source code today and I came across … Continue reading →

Posted in CoCo Programming | 8 Comments

Defender Conversion for the CoCo 3 – Part 1

Posted on December 31, 2017 by nowhereman999

Hello, I wasn’t going to blog about my conversion of the arcade version of the William’s classic game Defender for the Tandy Color Computer 3 but I decided it might be nice to share some of my progress.  Especially when … Continue reading →

Posted in CoCo Programming | 2 Comments