The ROM monitor of the Netronics Explorer/85 computer allows the step by step execution of a user program. This is implemented with the help of the 8155 timer and the trap interrupt line of the 8085: the timer is set with a count such when the first user program instruction is executed, the processor is interrupted and the monitor kicks in to show part of the execution environment.
I don’t own the original hardware at this moment, but I would like to ask to somebody that owns it if this functionality really works.
My question pops up because I cannot make this work in an emulated environment, since the timer is being programmed with 197 cycles, but the launch function for the user program takes 211 cycles, so the program is always interrupted before starting the execution of the user program. In the monitor program listing you can find online, you can see that somebody else also annotated this, so I’m really curious in knowing if this feature ever worked correctly without patching the ROM:
Thanks in advance!