Why answer of uint8 in .m and mdl are different?

I have a value of -1.In .m file if i process uint8(-1) i get answer as 0,but in simulink if i feed a constant with -1 and use data conversion of uint8 i get answer as 255.Why do i get different answers.

Answer 1

[Walter Roberson]

http://www.mathworks.com/help/simulink/slref/datatypeconversion.html

Notice that Saturate on Integer Overflow defaults to Off; you want it to be On.