COMMON

Advances some ideas using Steve Wozniak’s 6502 SWEET16 interpreted byte-code language as inspiration. While the goal of SWEET16 was brevity, the goal of COMMON is functionality. The intent is to make a platform suitable for many commercial, scientific, and engineering applications.

For example:

• native type is equivalent to fixed-point decimal ±######.###
• easier support for banked memory
• easier support for higher language compilers
• arithmetic operations add, subtract, multiply, divide, and modulus
• inherent overflow/underflow detection
• all control branching is 16-bit relative, for easier relocatable code
• support for custom system/user functions, akin to INT in x86

Why 6502 and not, for example, x86?

• 6502 assembler is very easy and has a large archive of existing functions
• existing 6502 SWEET16 already has the “hard work” done
• interesting to see it run in newer faster versions of 6502 processors
• how do you think Bender does what he does? (or the Terminator!)

Completed:

• added all the instructions (see common/common.h for the list)

In progress:

• larger stack size, current stack size is only about 60 numbers, 250 or so would be better
• emulation of serial ports to allow standard I/O
• a unit test suite to ensure each instruction is correct
• a proof-of-concept application with decoupled system and application files

The meat of the project:

• common/common.h: details of instructions
• common/common.asm: assembler code for the instructions
• common/macros.h: macros used to define the interpreted byte-code
• common/appl.src: sample source file using the macros

Auxiliary:

• emulator/*: 6502 emulator (borrowed Mike Chambers’ Fake6502 CPU emulator v1.1 ©2011)
• xa-pre-process/*: my utility xapp to convert 32-bit fixed decimal quantities so that xa can use them

Right now, for testing purposes, the code builds everything into one file system.obj and runs the code in the last block loaded, in this case, the code corresponding to appl.src. Eventually will support decoupling of system and application files. Application files will be inherently relocatable.

To build and run:

make all
make run

The makefiles use re2c, flex, bison, gcc, cpp, xa, grep, and sed. Will eventually provide a ./configure.