VHDL is the worst designed language with the worst syntax that I have ever encountered. Why does this with-select-when code give me an error?:
library ieee; us
You have several syntax errors: The assignment should look like
with mux48sv select mux48ov <= mux48dv0 when "0000", mux48dv1 when "0001", ... mux48dv3 when others;