If you are talking about using TS credits to purchase a meal at a CS restaurant:
On the regular plan, maybe, and maybe not. It is not an official part of the regular plan that you can do this, although special exceptions were officially announced for certain times of year in the past. You will likely have better luck doing so at a resort CS than you would at park CS with the possible exception of the Main Street Bakery.
If you are talking about using CS credits to purchase a meal at a TS restaurant, that can never be done.
On the deluxe plan, the dining credits are fully interchangeable for TS or CS.