Quote Originally Posted by lerameur View Post
Ok , he is doing in the program the following:
sending
0 0 1 1 1 0 0 0 to portA
then
0 0 0 0 1 0 0 0 to portA
then
0 0 0 0 0 1 1 0 to portA
then
0 0 0 1 0 1 0 0 to portA

how do we know which one is which (DISPLAY OFF,
ENTRY MODE SET etc...)

k
Get a datasheet for nearly any parallel input LCD (Hitachi 44780 controller chip) and match the bit positions on PortA in the program with the bit positions in the LCD's datasheet. They will match up as long as you have a decent datasheet.