Operation
It looks like Nate has validated my statements above, and I was tempted to call it a hokey delayed start feature but you don't ever get to delay Pots/Pans. The delay is shortest for Normal, longer for Light, and even longer for Rinse/Hold. This is one of the things that aggravates me about my Thermador's sequencing on partial cycles. The water is no longer hot if I wait for the timer to advance on its own before the first fill.
I don't know if the 23 series shares the same cycling with the 21 series. If it does, I have a PDF of the 21's instructions (thanks Bob!) complete with a matrix of washes and rinses associated with each push button, and can shoot you a copy.
IIRC, for the Pots/Pans and Normal cycles you can fill both cups if desired. If you only want to fill one, it should be the "main wash" cup, which is the one with the cover, and you should close the cover. For the Light cycle, you never fill both cups; fill only the main wash cup and close the cover.
I think that starting with the 21 series, there was no longer a heating delay. I'm guessing here, but I think the older models (series 20 and earlier) that have the heating element down in the recessed area by the filter are the ones with heating delays.
To answer Gary's question about selecting the Pots/Pans button but setting the dial to "Light," there are two possible scenarios based on the sequence of events.
Scenario 1: Turn the dial to Light and latch the door (or you can reverse that order, presuming all buttons are popped out as a result of door having been open). Push Pots/Pans button. Machine will start and will execute the Light cycle regardless of Pots/Pans having been selected.
Scenario 2: Latch the door. Push the Pots/Pans button. Machine will start. Advance dial manually to Light cycle. You'll hear the machine stuttering its way through split- second wash, drain and fill actions as you move the knob around. Not recommended. Had the user selected the "Light" button, none of that stuttering would have taken place. The "Normal," "Light," and "Rinse/Hold" buttons do nothing more than disable the timer and prevent functions that would normally occur ahead of them if any of the buttons to their respective left had been selected instead.