Lpc2000

Just to chip in as well, I have never had a problem with 5V 232 chips at 
any baud-rate etc. The fact that you measured 2.3V when you used a 
series resistor indicates that you should perhaps check your 3.3V 
supply. Perhaps you have damaged these inputs because the 5V was present 
when your 3.3V supply was still ramping. The 5V tolerant inputs depend 
upon the 3.3V supply being present to operate effectively. The chips do 
work as they are spec'd, you need to look at your implementation.

Is your VDD supply at a nominal 3.3V and is it clean? Is your 5V supply 
the same? What do they look like (ramping) when power is first applied? 
I think if you scoped the inputs on both sides you can get a clear 
picture of what is really happening anyway.

*Peter*

Gus wrote:
> On my board I have LPC2138 connected to MAX232 running at 5V. I had 
> problems with UART until I added a 4.7K resistor in series. and the 
> voltage high on it now is 2.3V
>
> Are the pins real 5V tolerant? The data sheet says UART RX is 5V 
> tolerant!!!
>