Lpc2000

Dear sirs 
I met a very strange situation. I use LPC2105 in my simple test 
board, that has only a MAX3232 to connect to PC. I want to download 
program through this port. But when I use LPC210X to read the part 
ID, I got the failed message. When I use an Oscilloscope to watch the 
CLOCK and UART0 signal, the communication was successful, the ISP 
software got the part ID 4293984034 and the boot loader ID 1.3. Is 
this correct? I repeated several times. the result is -- 

1. power on the board then place the probe --- always fail 
2. place the probe then power on --- almost successful every time 
3. after successful connect, it will always be successful even if 
remove the probe. 

I guess it may be caused by the sequence of inner power and IO power. 
But no matter I power on the 1.8v or the 3.3V first and then the 
other, The board does not work. 

Who knows this reason and help me please. 

Richard

--- In lpc2000@yahoogroups.com, "painfulcn" <painfulcn@y...> wrote:
> Dear sirs 
> I met a very strange situation. I use LPC2105 in my simple test 
> board, that has only a MAX3232 to connect to PC. I want to download 
> program through this port. But when I use LPC210X to read the part 
> ID, I got the failed message. When I use an Oscilloscope to watch 
the 
> CLOCK and UART0 signal, the communication was successful, the ISP 
> software got the part ID 4293984034 and the boot loader ID 1.3. Is 
> this correct? I repeated several times. the result is -- 
> 
> 1. power on the board then place the probe --- always fail 
> 2. place the probe then power on --- almost successful every time 
> 3. after successful connect, it will always be successful even if 
> remove the probe. 
> 
> I guess it may be caused by the sequence of inner power and IO 
power. 
> But no matter I power on the 1.8v or the 3.3V first and then the 
> other, The board does not work. 
> 
> Who knows this reason and help me please. 
> 
> Richard

Do you have capacitors around your crystal? My board has a 15pF 
capacitor to ground on each side of the crystal. It could be that the 
oscilloscope is providing the capcaitance needed to start the 
oscillator.

-- Charles

At 03:07 AM 3/22/04 +0000, you wrote:
>Do you have capacitors around your crystal? My board has a 15pF
>capacitor to ground on each side of the crystal. It could be that the
>oscilloscope is providing the capcaitance needed to start the
>oscillator.

Or possibly power supply decoupling?

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,
be they legal, genetic, or physical.  If you don't believe me, try to
chew a radio signal. "

                         Kelvin Throop, III