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Williams Level 7 Programming Manual

Copyright © 2000-2005 Jess Askey
Document Version 0.37 11/25/2004

Version History

0.36 - Changed formatting to better fit page. Fixed broken links to text files.
0.37 - Updated documentation quite a bit, expanded all sections, added overview and update docs on new MACROS.

Preface:

This manual covers extreme detail of both the hardware platform and the Level 7 Pinball Operating System Software used by Williams Electronic Games between the years of 1980-1984. Using this manual along with the Level 7 Flipper Program should allow you to program your own game ROM. I highly suggest that you visit my Level 7 Pinbuilder page for other information and assembler tools if you want to undertake this project.

Table of Contents:


General System Overview:

The Williams Level 7 System was part of an evolving group of firmwares that Williams used on all their electronic pinball machines. Beginning with Level 3 and growing up to Level 11C, they built upon the designs of previous operating systems to improve and enhance their games. The time period when Williams was using the Level 7 OS is considered the point at which Williams left the competition behind in technology. At the time, no other manufacturer could match the complexity of any Williams game. The programmers that designed the Level 7 System (Larry DeMar,???) created an operating system at is extremely fast, efficient, small and powerful. At a time when ROM space was quite expensive, they managed to pack lots of versatility into 2 2716 ROM's. One for the OS and one for the game. Given the cost of ROM space, this allowed them to spend more money on the game design.

The Level 7 CPU was used on 18 games produced by Williams.

The software in Level 7 games is made up of two parts... a Flipper Program (in this case, the Level 7 Flipper ROM's) and GAME program. The basical design of the Level 7 OS is a framework for a game, it contains all the background code to manage the game. All GAME specific information is contained in the GAME ROM's. This data defined in tables and larger sections of code to react accordingly to switch closures. Because the OS was not nearly as fancy as newer systems such as WPC, you basically only need to define system, lamp, and sound tables and then implement code for every switch event. That is it. Using this manual and other resources on this site, you should be able to build your own GAME ROM's without much knowledge of how the actual OS works. Sort of like how millions of Windows users seem to be able to produce windows apps without knowing anything about what goes on under the hood. ;-)

I have been working on this for about 5 years now and Im glad that I may actually be able to start designing my own game in the near future instead of staring at disassembled code for hours on end. I hope this will educate pinball collectors that like to learn more info than the average guy. Maybe we will see more home games produced as well. Have fun!


Hardware:

The hardware of the Level 7 pinball machines built upon the existing Level 6 platform. The CPU was a Motorola 6808 processor running at 1MHz. Input/Output operations are handled by five 6821 Peripheral Interface Adapters, six in the case of Hyperball. The RAM space is supplied by a pair of 2114 (1K x 4) chips. These replaced the dual 6810 (128 x 8) RAM chips. The following improvements were made to the system...
  • 768 bytes of Additional RAM space (1K Total)
  • 4K bytes of Additional ROM space (12K Total)
Typically only 8-10K of ROM space was used on production games. The quadrupling of the RAM space was probably the most important upgrade as it allowed the programmers to create a much more complex software structure and also allowed player data carry-over from ball to ball. A very important step which helped make the game flow across it's entire play length instead of having distinctly seperate ball-in-play rules.

Software:

 
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