it is not 16 bit lcd ... it is 16X2 lcd...
lcd in 4 bit mode uses only 4 data lines and it will be connected to port pins. other 4 data lines in LCD are grounded
in 8 bit mode 8 port pins are used to connect all 8 lines of lcd data lines...
in both case Rs , r/w and en pins are required.
---------- Post added at 19:59 ---------- Previous post was at 19:57 ----------
in 4 bit youcan transfer 4 bits of data.. and 4 bits next time. so you need to shift the data to proper pins and send it.
mask the 4 LSB and send 4 MSB nibbles. the mask 4 MSB nibbles and shift data to suit the data pins of controller and send it.