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Linking ROM Routines in Sixty5o2

Source: https://8bitnews.io/

For those who own the BE6502 and use Sixty5o2 as it's operating system, there is a short update. Today we added a number of changes, that were provided by David Latham. Big Thank You, David!

He realized, that VASM is actually able to spit out addresses of routines and labels during the assembly process. Simply adding a command line switch during the assembly of the bootlader, one can generate a symbol list:

vasm -dotdir -Fbin -L bootloader.lst bootloader.asm -o bootloader.out

This allows to outsource often used routines into the ROM - there is plenty of space. Afterwards one can simply 'link' against these routines, by jumping to their respective addresses from a program im RAM via 'jsr'. Check David's example program for details.

This way you can make use of existing ROM routines easily, as well as add your own ones and keep your programs in RAM small.

If you check that out, please be aware, that we also changed the default behaviour of the mini keyboard. We now assume, that you built the BE6502 according to Ben's schematics and all buttons are tied high normally, and get pulled low when pushed.

Happy hacking!

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