This chip has two voltage output 8-bit D/A

I want them to work as a standard linear D/A, but they have sort of inverse
S-curve function, like this:
     __/
    /
Somebody might have already made a routine to convert a byte value to a
corresponding output where each bit change is always the same voltage change?

Thanx in advance
/Morgan

/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  mrt@iname.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /