There is no limit down in cash forex
Trade continues in forex despite the closing of futures tade due to limit locks
(its not actually closed, I explained here: US equity futures circuit break triggered - ES limit down)
FX has no such restriction, the chaos is expressed in wild swings (USD/JPY range today has been over 300 points, and others have been wider still) and wide spreads.
No limit down. No limit up.
USD/JPY chart. daily candles: