Lpc2000

I use LPC2134 to control a LCD with 5V voltage supply and KS0108 
controller. P0[27:31] act as the five control pins. P1[23:16] act as 
the date pins. Now I found the voltage of the eight date lines is not 
correct, stays in 2V when high, and 1V when low , which leads to data 
chaos. 
I want to know:
1. How to deal with the interface circuit with a 5V device?
2. The datasheet of LPC213X said, there are pull-up circuits in P1
[23:16]. I want to know the deal circuit of these 8 pins.

Thanks!