topic Re: a LPC54xx main clock issue. in LPC Microcontrollers

a LPC54xx main clock issue.

yy0824_2006 — Mon, 07 Jan 2019 05:46:55 GMT

what i did :

1. i set the lpc54606 main_clk:48Mhz

2. I initialize a GPIO as output, then in main i did this:

so i got a clk . but the frequency is 750khz according to my oscilloscope. I think it should be 24Mhz . Why?

forgive my poor English.

thanks.

Re: a LPC54xx main clock issue.

converse — Mon, 07 Jan 2019 13:04:53 GMT

Because you are executing MANY more than a single instruction when calling the function GPIO_PortToggle. Assuming that you have set up your clock correctly, I'd calculate that you are executing approx 15 instructions to toggle the GPIO.

Re: a LPC54xx main clock issue.

Alice_Yang — Fri, 11 Jan 2019 03:10:55 GMT

Hello yangyong wu ,

Yes, as Con Verse said, the function " GPIO_PortToggle" not only one instruction.

You can check the instructions on Disassembly view. For MCUXpresso IDE example, you can open it as below:

Hope it helps,

Have a great day,
TIC

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