W might normally be connected to E so that memory bank W is available for the Cassette Interface Adapter (e.g. to load BASIC from tape into bank W). I have a different configuration: W=>1 and S=>E, so that I can use my BASIC firmware card instead of loading from tape.
Note that S, T and R are "user selectable" chip selects, of 4k each. In my configuration, S is used as the chip select for the BASIC firmware card.