This took a lot of tinkering and quite a bit of frustration too, but I’ve finally got Direct working with new EPROMS that I wrote myself.
Going through a lot of issues with various assemblers (being on a Mac) and not knowing all the details obviously of coding ASM for Motorola which is still quite different from Assembly on Intel (which is something I haven’t done in say 20 years either), burning through a milion EPROMS only to each time find it didn’t work got a bit annoying.
However, major thanks to user Steven on Hackaday.io, who created some interesting Motorola projects himsef, I was able to create a working workflow and have my first diagnostics EPROM running that produces 3 little beeps when starting.
I already know that, at least the majority of the hardware is OK, but now that I know this works, it’s PLAY TIME! There is so much space left if I use the original bootloader, I think I’m just going to write diagnostics routines and add them to the boatloader.
I can write simple tests for all the midi ports output, display and buzzer. But let’s start small, and now focus on the Display.
Having the ability to create new working boot roms, also opens up a 3rd possibility to load the OS on the system. There is a simple RS232 serial port built in and I can use that with a serial to usb to try to pull the OS in. Sounds easy enough – it isn’t, but the possibilty is there.