On Mon, 5 Feb 2024 19:16:46 -0000 "Rob Jarratt" <[email protected]> wrote:
> Your annotated VT100 listing was invaluable in helping me to fix my > own VT100 (still not working though, but on the video output side). > Would be interested in how you did it, I get the impression from your > message that you used an emulator to observe the behaviour? The main write-up on that is here: https://vt100.net/dec/vt100/rom/how (which I am always prepared to revise, if something doesn't make sense!) I started with MAME, because it supports VT100 emulation with the exception of smooth scrolling, and because it has a really excellent debugger. However, I had to switch to my own program based on Nicolas Allemand's 8080 core in the end, for two reasons: 1. I needed to stimulate the terminal with serial inputs and key presses and observe the serial outputs, and 2. I needed to know that I had covered the entire ROM, so I combined the 8080 core with a coverage checker, to mark all reads, writes and DMA accesses to RAM while it worked its way through a file that contained stimulation instructions: "pause", "keyboard character", "serial input", etc. Coverage checking might sound bizarre, but I had some code that I disassembled, understood and documented and could not for the life of me work out why I couldn't provoke it into executing; it turned out to be a bug in the firmware. Regards, Paul
