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!

Umm...  I do not know anything about KS0108.

But I think your LPC2134 and LCD controller could be trying to 
drive the bus at the same time.   Else it should be:
-  logic level of 0V/3.3V when bus driven by LPC2134, or
-  logic level of 0V/5V when bus driven by LCD controller.

The pullup resistors on LPC2136 are weak pull in 50-100KR.  
Unfortunately, there is no equivalent I/O pin circuit provided by
Philips.

So far, most of the external CMOS interface (with logic threshold
level at 2.5V) are working fine with the LPC2xxx 0V/3.3V driving
outputs (direct connection).

Regards



--- In lpc2000@yahoogroups.com, "angelazhu_china" 
<angelazhu_china@...> wrote:
>
> 
> 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!
>