Portal-9 6809-6309-CoCo-Vectrex IDE for Windows Description:

Write 6809/6309 machine-language software, build ROM images, virtual disk images and more, integrates the M.E.S.S. emulator system for a full WYSIWYG environment. You can literally build your software and see it run on your PC before exporting it to the real destination machine. Write software for any 6809 or 6309 machine, including the Tandy CoCo, the Vectrex, and others. The built-in assembler is smart enough to adapt to various popular types of 6809/6309 source code. This IDE is well worth the low price.