You're right about the active state of nPSEN. There's a reason why there's a bar over that signal in "the bible."

However, the state that matters with ALE is the "active" (high) state, i.e. the positive state, during which data is to be propagated through the address latch. It's the signal that enables the sampling of the low-order address byte from P0, according to "the bible" (I just checked the "family architecture" section just to make sure I wasn't nuts (at least in this respect).

If power-down was not intended to allow corruption of external RAM, I'd suggest that it's very important to ensure that nRD and nWR are never active during idle or power-down. Once that's done, it shouldn't matter at all what happens on nPSEN or ALE.

RE