SUBLEQ, revisited

January 29th 2012 at 10:09pm

Finally got around to finishing the writeup on a small test program for the SUBLEQ-oisc. Not terribly complicated, but it's a first step while I sort out my academics and my summer plans. Developing a small assembler for a SUBLEQ system is complicated by my breaking of the address space into two discrete sections of Instruction ROM and RAM. I did do this for simplicity's sake, and will be looking into taking out the IROM and replacing it with a unified address space, but to do that means moving up to 16-bit addressing and adding three additional CPU states to fetch operands from memory separately. I'd held off modifying the microsequencer until I'd finished the assembler (and maybe looked at writing a small C-like language interpreter using yacc and flex, but time is a huge limiting factor for now.) It's entirely possible that I'll just go ahead and finish a small assembler that's pretty rudimentary, modify addressing (and maybe look into relative addressing) and then tackle the C-esque language. EBNF grammars are something I want to sit down and have a readthrough, and my school calendar doesn't quite allow for that yet.