The tower shield description (PHB, pg. 125) says that the user can utilize it to gain total cover, while giving up all of his attacks. How exactly does this work?

Let's say a dwarf using a tower shield is fighting a single enemy. The dwarf gives up his attacks and uses the shield for total cover. I presume that means the enemy cannot attack him at all, since you can't attack a target with total cover (PHB 152). Correct?