Brad Rodriguez

Moving Forth - Internals and TTL Processor Brad Rodriguez

In 2018 we have 50 Years of Forth. When I looked for a new project for an eBook I realized that one area is not very well covered: How do the Forth internals work? How can you build a Minimal Processor executing Forth directly? How do you write an Assembler in Forth? When I looked around for some documentation, I remembered this series of articles again. They seems to fit very well together. I contacted Brad and asked for permission to publish them as part of the Forth Bookshelf. He liked the idea so I started formatting. I did not change any of the original material. The only part I added was an appendix, where I redid some of the pictures, so I could understand them better. As in many cases, additional material can be found on the Forth-eV.de Wiki, and we will start with the appendix added here, and what else we might come up. I have to thank Brad Ridriguez for the copyright to publish this documentation. Enjoy reading and any feedback please send to epldfpga@aol.com. From Brad: Everyone in the Forth community talks about how easy it is to port Forth to a new CPU. But like many "easy" and "obvious" tasks, not much is written on how to do it! So, when Bill Kibler suggested this topic for an article, I decided to break with the great oral tradition of Forthwrights, and document the process in black and white. Over the course of these articles I will develop Forths for the 6809, 8051, and Z80. I'm doing the 6809 to illustrate an easy and conventional Forth model; plus, I've already published a 6809 assembler [ROD91, ROD92], and I'll be needing a 6809 Forth for future TCJ projects. I'm doing the 8051 Forth for a University project, but it also illustrates some rather different design decisions. The Z80 Forth is for all the CP/M readers of TCJ, and for some friends with TRS-80s gathering dust.