Hi there,
Because 8051 is a general MCU model in Multisim. It is very hard to predict and calculate the power consumption by simulation, especially during high temperture situations. In addition, there are lots of Manufacturers who provide MCUs based on 8051 core. For exmple, Atmel 89c51/s51, Intel MCS51,STC89C51 etc. If you use simulation tools to calculate the power consumption, it's gonna be very inacurate.But I can give you a general advice to calculate the power consumption in reality.
Typically, the P_MCU = P_internal + P_IO + P_Analog
The P_internal depends on the working frequency and working mode(active, sleep, idle etc)
P_IO and P_Analog are the power consumption for digital ports and analog ports respectively.
Here are some links and files might be helpful to the calculation of power consumption:
http://www.embedded.com/design/power-optimization/4395689/Optimizing-for-low-power-in-embedded-MCU-d...
Chen_T
National Instruments
