If I reveal emperor's divide in my main phase, are my units readied in base?

Yes — your units stay ready. Emperor's Divide ("Move any number of friendly units at a battlefield to their base") has no instruction to exhaust them, so they arrive at base in whatever state they were in — ready units remain ready.

This is different from a Standard Move (Rule 144.2), which costs exhausting the unit. Card-effect moves like Emperor's Divide don't pay that cost unless the card says so. If the unit was exhausted at the battlefield, it will also arrive exhausted.