"Functioning" is not an object and cannot be encountered, to assume the mind is substance is the category mistake made, and why people leap to something non-physical: if it must be a substance it cannot be physical, for sure.
As for "completely simulated", I do not believe that computers - as we now use them - are capable of "simulating" a mind. The mind is much more than symoblic processsing: it attaches meaning to information, creates relations between itself and the world, (amongst many other things). These phenomena are not information processes and cannot be achieved by Linear Regression (to characterize Machine Learning accurately enough).
It is important to point out that any scientific explanation of consciousness is going to be unsatisfyingly reductionistic. Science significantly reduces experience to a "substance model" where everything can be modeled as substances in motion ... and thus the mathematical edifice which results is completely devoid of the vast majority of information which one acquires: the sound of the cannonball as it his the grass, its colour, significance, etc.
The vast majority of our experience which we may hope to explain is discounted (necessarily so) in order to be scientific (predict what our next experiences will be like).
There will be an increasing number of "explanations" of various aspects of mental functioning based on the structure of the brain, I doubt any of these will provide anything more compelling than what we have currently.
There are "brute certainties" (brute facts) which are undoubtable and the starting point for all investigation, scientific or otherwise. This brute fact is experience, or more accurately, the world of signficance, relations, awareness, etc. in which the self as well as everything else is embeded within.
Explanation proceeds as generalization, taking one aspect of Experience and generalizing to some general property of Experience: pens fall, all objects fall, all objects in gravitational fields fall.
There is nothing we can appeal to in accounting for Experience itself: there is nothing else available. Explanation has to end somewhere, and that is the final - and only tenable - reply to the question of our conscious experience.
I would like to read about this where to begin?