Black-box simulation is useful at times, but, if you want to know how long something takes, or what the count in the counter is after the execution of a given instruction, or how some other part of the gross logic, as described in the datasheet, associated with serial I/O, parallel I/O or the timer/counters, etc, are behaving at any given time with respect to the code, i.e. when, exactly, it samples the serial port, they're often of little help. There are several readily available simulators of that sort. A more detailed simulator, capable of tracking all documented functions in a given MCU would be much more useful.

The KEIL folks once told me that such a simulator was not even possible, as the external memory interface was not deterministic, which certainly was incorrect.

Their simulator or whatever it is supposed to be was taken off my list at that point.

I once had a development program, distributed at no cost, from a fellow in Massachusetts, U.S.A. that kept track of the counter state and so on in an 8048. I don't remember whether it computed the number of cycles from start to "here" but I doubt it would have been difficult.

What would really help would be a clock-cycle-by-clock-cycle simulator that kept track of counters, timers, serial port(s) external memory bus state, if one was in use, and read a schedule file for external inputs. That would be helpful in a lot of cases where something was known about the character of the simulated MCU's external environment and task.

RE