Its not unreasonable to assume that a d/w and g/d may be used at the same time.equipment nor luminaires, only fixed in place devices corded or hardwired, no such 80% exclusion exists in those sections either for fixed-in-place appliances. Both of devices/equipment described in Harry's example: the DW (fixed in place) and the Disposer (either hardwired or cord-and-plug) are not prohibited from sharing the same 20 Amp circuit, as long as there are no luminaires or non-fixed-in-place devices sharing it according to the citation Harry apparently was referring to. Also, if the example disposer (9.8 A equal to or less than 50%) was the only fixed in place, and the dishwasher was portable (not fixed in place) and corded, as long as the DW didn't exceed 80% of the entire circuit rating, it too would not be prohibited according to these sections, although it would not be permissable to operate both at the same time if the combined load equalled greater than 100% of the branch circuit's rating.
Key to this discussion applicable to the original poster, is that the receptacle's face must be rated for 20 amps and that the switch the OP utilizes be of a sufficient rating for the disposer.
I think raven was reffering to 210.23 (a)2 utilization equipment fastened in place... it goes on to say.. Totalrating..shall not exceed 50%..
this would be considered cord and plug fastened equipment since we were talking about wiring a device ...
I think everyone is aproaching the same conclusion from a different perspective. there is no need to split hairs over why we agree.