How is the drain-current calculated from an N-Channel MOSFET, when you specify from datasheet?

Hello,

i'm writing my bachelor thesis at the moment. I use the model of an N-Channel MOSFET from the Toolbox SimElectronics. In the help is only a description,how the model calculates the drain current, if i use the option "Specify using equation parameters directly".

How does the model calculates the drain-current, if i use the option "Specify from datasheet"?

I tried to find some information about the Shichman-Hodges equation, but i did not find anything about this calculation with the parameters from the datasheet.

Thank you for help

Max