There's no fixed number of AS levels required for admission to a Canadian university. Canadian universities don't use the AS level system as a primary qualification. They primarily look at the equivalent of a high school diploma or its international equivalent (like the IB diploma). Some universities might consider AS levels *in addition* to your high school transcript as part of your application, but they won't be a stand-alone requirement.
To find out the specific requirements, you must check the admission requirements for each university and program you are interested in *directly on their website*. The requirements vary significantly between institutions and even between different programs within the same university.