Some commands that worked at ModelSim do not work at QuartusII

I should have made it clear that you can't ever nest a @(...) construct inside another. The @() is almost always "always @(some_clock_edge) begin <code> end" For best performance <code> should be something that can be done in 1 or 2 levels of logic. It doesn't make sense to say "when there is a clock edge, wait for a clock edge." like your code would imply. To do what you seem to have in mind in your original post, you can check that rdy is high (or low) when there is a clock edge as I've written above.