locales such that the associated topos is subdiscrete?

CAUTION: The Sender of this email is not from within Dalhousie. Toposes Sh(B) of sheaves over a cBa B have the property that every object appears as sum of subterminals. Does any one know a more elementary characterization of those cHa's A such that every object of Sh(A) appears as sum of subterminals? Maybe it is precisely the cBa's but I do not see how to prove it... Thomas [For admin and other information see: http://www.mta.ca/~cat-dist/ ]