Morrison made the move to the former Premier League side last week, with Cardiff boss Ole Gunnar Solskjaer watching the defender in action on the opening day of the Championship season before completing the deal.
"I knew something was on the cards, but I trained with Reading on the Thursday morning and was then told to go to Cardiff. I was having my medical a couple of hours later," said Morrison, according to Sky Sports News.
"From the moment I heard about Cardiff's interest I was dead excited.
"Cardiff are a club heading in the right direction, they have a young, hungry manager and from what I've seen it's a great squad. The quality is endless with the players they have in every position."
Cardiff currently find themselves in fourth place in the Championship table.