AnsweredAssumed Answered

Is 48MHz PWM possible using SCT on LPC4357@204MHz?

Question asked by quex on Jun 13, 2018
Latest reply on Jun 14, 2018 by Kerry Zhou

I'm currently struggling with the SCT, which I need to use for PWM generation.

I tried the LPCopen function:

Chip_SCTPWM_SetRate(LPC_SCT_T *pSCT, uint32_t freq);


It calculates a rate and writes it to the match reload register 0:

rate = Chip_Clock_GetRate(CLK_MX_SCT) / freq;

Chip_SCT_SetMatchReload(pSCT, SCT_MATCH_0, rate);


The chip clock is 204MHz and the requested PWM frequency (freq) is 48MHz.

204 / 48 = 4.25

The decimals are of course lost and I end up with a frequency of 40.8MHz (204 / (4+1))

The next step I can reach using this function is 51MHz.


Is there a way to get 48MHz output frequency using directly the SCT registers, without LPCopen?

Thanks for any hint.



The frequencies are not multiples, the clock can only be divided, there is only one internal clock source for SCT.
It's not possible to generate PWM @ 48 MHz.