Can I verify external 50 MHz crystal with LPC540?

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Can I verify external 50 MHz crystal with LPC540?

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jana_beck
Contributor II

Hi!
I am currently working on setting up a functional test for my application.
For one of the components I need a 50 MHz clock signal.
Is it possible to measure if this clock signal is correct using my MCU (LPC54016JBD100).

I am not very familiar with internal clocks, any help appreciated!

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jana_beck
Contributor II

Hi Jun,
thank you for the reply.
I am actually trying to do it the other way around, having an external clock (which is only used by another component, to be precise by a PHY) and verifying if the clock signal is correct with the MCU.

I am trying to have a functional test for my electronic assembly with as much measurements done using the MCU.

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ZhangJennie
NXP TechSupport
NXP TechSupport

You want to use LPC to measure an external 50MHz clock.

The idea is to use input capture feature to measure 50M pin. each toggle trigger a capture_counter+1.

You need also have an accurate external low frequency clock (Don't use internal FRO, it has 1% error), for example 100KHz, it trigger interrupt for each clock. then you can calculate "capture_counter" value.

the measured clock = 100Khz * capture_counter value

Have a nice day

Jun Zhang

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ZhangJennie
NXP TechSupport
NXP TechSupport

HI Jana

We can measure CLKOUT pin to check internal clock.

Using CLKOUTSELA to set the clock source.

Below diagram, main_clk can be measured by CLKOUT pin.

pastedImage_1.png

Hope this helps,

Jun Zhang

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