topic Re: CPU clock not visible on CLKOUT pin of LPC4088 in LPC Microcontrollers

CPU clock not visible on CLKOUT pin of LPC4088

sunilsawant — Tue, 04 Oct 2016 06:20:27 GMT

I am developing my application on LPC4088 MCU.

I want to operate the CPU at 96 MHz.

I have programmed the Clock and System Control block to generate the CPU clock frequency at 96 MHz.

However, CPU clock is not visible on clkout pin.

How can I view cpu clock on clkout pin of LPC4088.

I have attached clock initialization code for clock and system control block.

Please suggest suitable solution to the problem.

Original Attachment has been moved to: drv_clock.c.zip

Re: CPU clock not visible on CLKOUT pin of LPC4088

vicentegomez — Tue, 04 Oct 2016 21:07:33 GMT

You can check the LPCOpen code for the 4088 "periph_clkout"

Normally this code is install on the LPCXpresso folder

C:\NXP\LPCXpresso_8.2.0_647\lpcxpresso\Examples\LPCOpen\lpcopen_2_10_lpcxpresso_ea_devkit_4088.zip

I hope this will help you.

Re: CPU clock not visible on CLKOUT pin of LPC4088

sunilsawant — Wed, 05 Oct 2016 07:41:24 GMT

Clkout example in LPCOpen code uses LPCOpen libraries. I want to write code using registers without using libraries.

Re: CPU clock not visible on CLKOUT pin of LPC4088

vicentegomez — Thu, 06 Oct 2016 16:29:27 GMT

I believe that you have missing to set the PINSEL3 for the CLKOUT function

Regards

Vicente Gomez

Re: CPU clock not visible on CLKOUT pin of LPC4088

jbr — Mon, 05 Mar 2018 00:21:12 GMT

You need to configure the pin using IOCONx.

You probably don't need to wait for PLL0STAT to become 0x509, just feed in the new dividers and wait for it to stabilize.

CLKOUT is limited to about 50MHz... so you should set a divider in CLKOUTCFG. Just divide it by 8 for a nice 12MHz output. Easy to feed into a counter or check with a passive scope probe.