LPC84x - how to read FRO frequency programmatically

[pepoja]

Hello all,
In others LPC microcontroller I can determine the input frequency to the core and to the peripherials from running application.
But in the LPC84x series I don't know how.
Fro can be 30 MHz/24 MHz/18 MHz and I able to set it by set_fro_frequency API call.
But how to read it?

Thanks.

[pepoja · Accepted solution]

Thank You for your quick reply.

Yes, I know UM11029.pdf of course.
Due to the minimalization components count, I don't use external clock input/external crystal.

For my applications was FRO good solution. I was think....
All application timing is based on it. I must to know the input frequencu to clock generation engine.

Finnaly solution is:
Write desired FRO frequency by API call after each MCU reset.

p.s. Why API doesn't include get_fro_frequency also? It's a unbreakable problem?

Petetr

[xiangjun_rong]

Hi,

Unfortunately, there is nowhere to read the clock for the core and a specific peripheral directly.

Pls refer to section 8.5.1 Clock generation in UM11029.pdf, the application code can define the external crystal clock frequency or the clock frequency from CLKIN pin, then read the clock source mux and divider register to figure out the core clock frequency and peripheral clock frequency.

BR

XiangJun Rong