Video Dromedary Processor

Now that we have a working Forth environment running on the SG-1000, it makes some sense to start building up the video display capabilities. Can I get sprites working on the TMS9918 for the first time in my career? Sticks and stones may break my bones, but words can configure a raster. Basic words To start with, I wanted to build up from the basis of controlling the video chip. On the TMS9918A, the vast majority of functions are controlled through altering tables in the video RAM. Because the TMS9918A comes to us from the Texas Instruments TI-99/4A, access to that VRAM is not memory-mapped. There’s ways to do that – Sega, in fact, did it on some arcade hardware – but the SG-1000 is not empowered to do so. The only way to access video RAM is one byte at a time through an I/O port. Therefore, the first thing to do is to create some basic words for writing and reading to the VDP. I’ve called these VDP! and VDP@ respectively, in keeping with the nomenclature developed by the PC! and PC@…