Surely 2 different mod states to consider here.
For the early 320's follow the checklist which starts with an attempted reset of both generators, if that is unsuccessful then you are stuck in emergency electrical config and an APU start is not reccommended.
For later 320's and all (?) 321's an enhanced RAT is installed, in this case an APU start is allowed after 45secs have elapsed since the loss of both eng generators.
So the enhanced RAT gives the cozy feeling requested on T16, change was somewhare around s/n 1000 for the 320 I think.//