These are all the possible values for the IG_ISIS_TAG_FEEDORDER tag.

Values:

IG_ISIS_FEED_SIMPLEX_1_TO_N	Scan front 1 to n.
IG_ISIS_FEED_SIMPLEX_N_TO_1	Scan front n to 1.
IG_ISIS_SCANTYPE_FEEDER_REVERSING	Scan front and page is in reverse order.
IG_ISIS_SCANTYPE_DUPLEX_REVERSING	Scan both sides and page is in reverse order.