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simulators versus emulators

S

steve marchant

Jan 1, 1970
0
Having difficulty with seeing any difference between the two terms.Can
anyone offer definitions, both generally and in relation to, say,
microprocessors.
 
D

Don Taylor

Jan 1, 1970
0
steve marchant said:
Having difficulty with seeing any difference between the two terms.Can
anyone offer definitions, both generally and in relation to, say,
microprocessors.

A simulator is usually a software model of hardware running a program.

An emulator is usually a hardware model of hardware running a program.

A software model can assume, for example, that you have a good clock
signal getting to the processor. It can assume that any input logic
levels have sufficient voltage and current, don't bounce, all the
usual things you might assume to be true. The free PIC simulator
provided by Microchip is a good example. It assumes a variety of
things and your code can seem to run fine. Then when you toast a
part and drop it into your board it doesn't run, because one of those
assumptions wasn't valid.

Software models may also run at a tiny fraction of the real speed
of the actual hardware, but this doesn't always have to be the case.
That can cause grief when you are attempting to deal with real-time
signals, timing constraints, interrupts that must be serviced in
a fixed small amount of time, etc.

A hardware model should act exactly like your real hardware processor
does. In reality there can be tiny differences there too. But it
usually is able to run at full speed and deal with more of the ugly
reality of the signals that you are connecting directly to the
hardware. But by being built out of more complicated hardware than
the bare processor it can also allow you to set breakpoints, record
execution for hundreds or even millions of clock cycles, observe
internal processor state, all without your needing to have your
program be modified to attempt to provide this.
 
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