There is no need to confine the address decoding for the LCD to address lines A12 and above. You can use address lines lower even lower than A8 if you provide enough pins to the decoder.

It is practical to wire the RS line of the LCD controller to the A0 line. Then wire the R/W line of the LCD controller to the A1 line. Finally use your PLD function to decode high order address lines to implement the two term type equation:

LCD_E = LCD_SELECT(A15:A14...Ax) * /RD
+ LCD_SELECT(A15:A14...Ax) * /WR

The use of the A1 line for the LCD read/write selection simplifies the design to meet the setup and hold times of R/W before and after the E pulse edge.

To write use addresses where A1 is low at a '0'.
To read use addresses where A1 is high at a '1'.

Micahel Karas