Atari 2600 Programming for Newbies

Session 2: Television Display Basics

By Andrew Davie (adapted by Duane Alan Hahn)

Table of Contents

Original Session

Hopefully you've been through the first part and have your editor, assembler, emulator and documentation ready to go. What we're going to look at now is a basic overview of how a television works, and why this is absolutely necessary prerequisite knowledge for the '2600 programmer. We're not going to cover a lot of '2600 specific stuff this time, but this is most definitely stuff you NEED TO KNOW!


Television has been around longer than you probably realize. Early mechanical television pictures were successfully broadcast in the '20s and '30s (yes, really!see The mechanical 'scanning' technology utilized in these early television systems are no doubt the predecessors to the 'scanning' employed in our modern televisions.


A television doesn't display a continuous moving image. In fact, television displays static (non-moving) images in rapid successionchanging between images so quickly that the human eye perceives any movement as continuous. And even those static images aren't what they seemthey are really composed of lots of separate lines, each drawn one after the other by your TV, in rapid succession. So quick, in fact, that hundreds of them are drawn every image, and many images are drawn every second. In fact, the actual numbers are very important, so we'll have a look at those right now.







The Atari 2600 console was released in many different countries around the world. Not all of these countries use the same television 'system'in fact there are three variations of TV systems (and there are three totally different variations of Atari 2600 hardware to support these systems). These systems are called NTSC, PAL, and SECAM. NTSC is used for the USA and Japan, PAL for many European countries, and Australia, and SECAM is used in France, some ex-French colonies (for example, Vietnam), and Russia. SECAM is very similar to PAL (625/50Hz), but I won't spend much time talking about it, as Atari SECAM units are incredibly rare, and little if any development is done for that format anyway. Interestingly, the differences in requirements for displaying a valid TV image for these systems leads to the incompatibility between cartridges made for NTSC, PAL and SECAM Atari units. We'll understand why, shortly!










All of this may sound complicatedbut really all we need to do is create a 'kernel' (which is the name for your section of an Atari 2600 program which generates the TV frame) which does the drawing correctlyand once that's working, we don't really need to worry too much about the TVwe can abstract that out and just think about what we want to draw.


Well, I lie, but don't want to scare you off TOO early. Wink


Next time, let's have a look how the processor interacts with hardware, I/O and memory.




Other Assembly Language Tutorials

Be sure to check out the other assembly language tutorials and the general programming pages on this web site.



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Session Links

Session 1: Start Here

Session 2: Television Display Basics

Sessions 3 & 6: The TIA and the 6502

Session 4: The TIA

Session 5: Memory Architecture

Session 7: The TV and our Kernel

Session 8: Our First Kernel

Session 9: 6502 and DASM - Assembling the Basics

Session 10: Orgasm

Session 11: Colorful Colors

Session 12: Initialization

Session 13: Playfield Basics

Session 14: Playfield Weirdness

Session 15: Playfield Continued

Session 16: Letting the Assembler do the Work

Sessions 17 & 18: Asymmetrical Playfields (Parts 1 & 2)

Session 19: Addressing Modes

Session 20: Asymmetrical Playfields (Part 3)

Session 21: Sprites

Session 22: Sprites, Horizontal Positioning (Part 1)

Session 23: Moving Sprites Vertically

Session 24: Some Nice Code

Session 25: Advanced Timeslicing





Useful Links

Atari Roots by Mark Andrews (Online Book)

This book was written in English, not computerese. It's written for Atari users, not for professional programmers (though they might find it useful).



Machine Language For Beginners by Richard Mansfield (Online Book)

This book only assumes a working knowledge of BASIC. It was designed to speak directly to the amateur programmer, the part-time computerist. It should help you make the transition from BASIC to machine language with relative ease.



The Second Book Of Machine Language by Richard Mansfield (Online Book)

This book shows how to put together a large machine language program. All of the fundamentals were covered in Machine Language for Beginners. What remains is to put the rules to use by constructing a working program, to take the theory into the field and show how machine language is done.



6502 Instruction Set with Examples

A useful page from Assembly Language Programming for the Atari Computers.

Continually strives to remain the largest and most complete source for 6502-related information in the world.



Guide to 6502 Assembly Language Programming by Andrew Jacobs

Below are direct links to the most important pages.



Stella Programmer's Guide

HTMLified version.



Nick Bensema's Guide to Cycle Counting on the Atari 2600

Cycle counting is an important aspect of Atari 2600 programming. It makes possible the positioning of sprites, the drawing of six-digit scores, non-mirrored playfield graphics and many other cool TIA tricks that keep every game from looking like Combat.



How to Draw A Playfield by Nick Bensema

Atari 2600 programming is different from any other kind of programming in many ways. Just one of these ways is the flow of the program.



Cart Sizes and Bankswitching Methods by Kevin Horton

The "bankswitching bible." Also check out the Atari 2600 Fun Facts and Information Guide and this post about bankswitching by SeaGtGruff at AtariAge.



Atari 2600 Specifications

Atari 2600 programming specs (HTML version).



Atari 2600 Programming Page (AtariAge)

Links to useful information, tools, source code, and documentation.




Atari 2600 programming site based on Garon's "The Dig," which is now dead.



TIA Color Charts and Tools

Includes interactive color charts, an NTSC/PAL color conversion tool, and Atari 2600 color compatibility tools that can help you quickly find colors that go great together.



The Atari 2600 Music and Sound Page

Adapted information and charts related to Atari 2600 music and sound.



Game Standards and Procedures

A guide and a check list for finished carts.




A multi-platform Atari 2600 VCS emulator. It has a built-in debugger to help you with your works in progress or you can use it to study classic games.




A very good emulator that can also be embedded on your own web site so people can play the games you make online. It's much better than JStella.



batari Basic Commands

If assembly language seems a little too hard, don't worry. You can always try to make Atari 2600 games the faster, easier way with batari Basic.



Atari 2600 BASIC

If assembly language is too hard for you, try batari Basic. It's a BASIC-like language for creating Atari 2600 games. It's the faster, easier way to make Atari 2600 games.

Try batari Basic

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Use any example programs at your own risk. I am not responsible if they blow up your computer or melt your Atari 2600. Use assembly language at your own risk. I am not responsible if assembly language makes you cry or gives you brain damage.


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