Toolchain: DASM & Stella

Mon, 01 Jan 0001 00:00:00 +0000

Toolchain: DASM & Stella#

Two tools cover the entire development loop for this book: DASM assembles your .asm source into a cartridge image, and Stella runs that image as if it were a real console.

Installing#

On macOS with Homebrew:

brew install dasm
brew install --cask stella

DASM is the de-facto assembler for the VCS; Stella is the reference emulator and an excellent debugger.

Assembling a ROM#

The canonical build command (from the repository’s xmas/Makefile) is:

Anatomy of a Minimal ROM

Mon, 01 Jan 0001 00:00:00 +0000

Anatomy of a Minimal ROM#

Every program in this book shares the same skeleton. Understanding these few lines means understanding what a VCS ROM fundamentally is.

The header#

 processor 6502

 include "vcs.h" ; TIA / RIOT register names (COLUBK, PF0, WSYNC, ...)
 include "macro.h" ; helper macros, e.g. CLEAN_START

vcs.h gives readable names to the hardware registers so you can write sta COLUBK instead of sta $09. macro.h provides convenience macros. In this repository both live in a shared top-level include/ directory that every game reaches via DASM’s -I../include flag — a single source of truth rather than a copy per game.