This would be done with the System Tick Timer or Systick. Please look into the code my colleague provided on the following community post: Re: Time elapsed - NXP Community
Just make sure to use the appropriate System Tick Timer, as the LPC55S2x has 3: "Two inside the CPU0 (Secured and Non-Secured), and one inside the CPU1 (Non-Secured)". For more information on how the Systick timer works, please look into Chapter 29 of the LPC55S6x/LPC55S2x/LPC552x User manual.
