Can LPC213X P1[23:16] act as the D[7:0] to a LCD with 5V supply?

Started by angelazhu_china April 29, 2006
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!

An Engineer's Guide to the LPC2100 Series

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 l..., "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!
>