Significance of bias when driving an LCD
You can map the commons and segments by using an old stepper motor - connect two flying leads from the motor to various connections on the lcd and twiddle the motor shaft to create a brief ac voltage.  As segments become visible, you map the connections and segments onto a sheet of paper. 

The data sheet for the PIC16F1939 gives the information about 1/2, 1/3 bias. Useful even if you do not use the inbuilt lcd driver peripheral in that particular mpu. 

Sorry but I have no experience with Atmel mpu and whether they even contain inbuilt Lcd driver facilities.  It will help to choose an mpu with an lcd driver peripheral already built in.