Lpc2000

Hello Gus,

LPC2000 samples every CAPx.y input in use at the rate of pclk. It 
takes two consecutive CAPx.y samples for a transition to be detected 
(i.e. if the current CAPx.y sample is high and the previous sample
was low, CAPx.y recognizes a rising edge). 

Assuming no jitter in the processed incoming signal and no jitter in 
the cclk/pclk clock, consecutive readings of the CAPx.y register 
content should not vary for more than 2 ticks in the worst case. The 
first uncertainty tick comes from the detection of the pulse's
leading edge, and the second uncertainty tick comes from the 
detection of the pulse's trailing edge.

What is the duty cycle of the signal you are processing? Do you use 
the same capture input to detect both rising and falling edge or you 
have two dedicated capture configured pins?

Regards,

Philips Apps Team



--- In lpc2000@yahoogroups.com, "Gus" <gus_is_working@y...> wrote:
> Hello,
> 
> What is the shortest pulse you can mesure on LPC capture module?
> 
> I am trying to measure some pulses using the capture hardware on
LPC 
> chips. The processor is running at 48Mhz and my capture module is 
> running at 1us/ticks
> 
> Connecting a function generator, I can read valid results up to 
1Khz. 
> When I go over 10KHz, the reading is not stable at all! About 10%
up 
> and down.
> 
> Thanks,
> 
> Gus