Notes
RemarksThe .dsk image below doesn't work in all emulators, due to the copy protection. In those cases:
Firstly, the disk has to be set to auto-load. If the disk is loaded by pressing Enter for Load on the +3 start-up menu then it won't work, as the I-register will be set to $3F and the decryption routine will give the wrong result. With auto-load set the I-register will be set to $00 and the code will decrypt correctly.
Secondly, set a break at $8BE2: LD SP,$8000; step through that command then skip over the next two CALLs and jump straight to the $8BEB: DI command, then Run and the DB1 start-up screen will be ready to use. I presume that the first CALL is the copy protection, as if it returns NZ (which it does) it makes the second CALL which erases all the memory and does a reset.