B was $FF and INCB called. Look at the Overflow Flag V
XRoad didn't set V, why?
... too many ideas and too little time ... Related stuff written in Python:
Dragon 32 emulator / PyDC - Python Dragon 32 converter: https://github.com/jedie/DragonPy
DWLOAD server / Dragon-Lib and other stuff: https://github.com/6809
B was $FF and INCB called. Look at the Overflow Flag V
XRoad didn't set V, why?
Xroar is right. The overflow condition is always related to signed value operations. For INC this happens only if 0x7f (127) overflows the positive value range and becomes 0x80 (128 or signed -128). Vice versa for DEC.
... too many ideas and too little time ... Related stuff written in Python:
Dragon 32 emulator / PyDC - Python Dragon 32 converter: https://github.com/jedie/DragonPy
DWLOAD server / Dragon-Lib and other stuff: https://github.com/6809