We have received a question on ARM Facebook I think this group could answer.
Is there any ARM Cortex-M microcontroller simulator available for free?
The poster seemed most interested about Proteus Virtual System Modelling I believe.
The best bet might be to download Keil MDK-ARM and use the simulator: Instruction Simulation in the Keil uVision Debugger
It can simulate program execution, as well as the whole system (including peripherals).
The limitations of MDK-lite are explained here
There are other options, such as QEMU, which is a generic simulator and can model an implementation of the Cortex-M3. It really depends on exactly what you're trying to achieve.
Hope this helps,
View all questions in Arm Development Studio forum