The one that immediately comes to mind that fits your area is Betty Corning (see link below). Since it is a viticella, it can tolerate the hot afternoon sun and it is fragrant in my garden. It also has a light colored flower that should show up against your dark colored wall. The only thing I am concerned about is the amount of sun that it will get in your garden. Could you elaborate on the number of hours of direct sun it will get in your garden, as well as the amount of indirect sun it might get over the course of the day? The reason I ask is that I have a few clematis that are not rated as being suitable for northern walls and they do well there. I think the reason for this is that although they might not get direct sun for most of the day, they do get quite a bit of indirect and reflected light.

Another clematis that is white and that has a slight jasminey fragrance in my garden is the integrifolia Hakuree. It is not the type of fragrance that will fill your garden with its fragrance but it is pleasant to smell up close.

Here is a link that might be useful: Betty Corning

Another integrifolia-type that is fragrant is Olgae. I have two of them and they are non-stop bloomers. As Miguel said, they won't be as aromatic as, say, a Casa Blanca lily but the scent is delightful, nonetheless. One of mine gets very little direct sun but year after year is a very good bloomer...probably about 75% of what the other one gets that gets 75% direct sun per day.
Tanya

Here is a link that might be useful: Olgae at Clematis on the Web (COTW)

Thanks for the great ideas, to elaborate, the position I have is against an east wall and gets about 3-4 hours of direct, midday sun, otherwise shade from a covered patio. This is a protected area so can grow a clematis that is zone touchy. On the trellis I currently have a don juan climbing rose, but it just grows like a weed and doesn't flower, so think is too shady for it. On the other side the clematis, ramona, keeps getting the wilt, so it must go and I am planning maybe a ampelosis or ? (maybe two clematis), I really want fragrance as this is closeby to where we sit. I probably need to make the trellis larger as well.
Here is a picture of the area.
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I'm also debating on putting in a hydrangea or rhodo beside the rose.

That's a pretty area. We share the same frog duo sitting on the bench. :) Yes, the trellis will have to be taller. I would recommend Betty Corning. I can smell that one when I'm in the garden and I don't have to be close. I have two of them but one is in only about 3-4 hours of sun. It does well. Since she's a fast grower and prolific bloomer, I would say you just need one of her. Her fragrance is heavenly.

Stay away from ampelopsis brevipedunculata. I had the variegated leaf one because it is supposed to be less vigorous than the all green variety and it grew to be a monster. It would eat your trellis in a heart beat. On top of that, as the vine matures it develops tons of nicely colored berries that the birds eat and deposit everywhere. As a result, you get babies popping up everywhere. Additionally, it draws japanese beetles from miles.