I'm working on a project using RT1062 and MCUXpresso IDE.
During the EMC test, the signal strength of 200Mhz was too high, so I wanted to use the spread spectrum function.
To use the spread spectrum, we set the spread spectrum by calling BOARD_SysPllConfigSpreadSpectrum() after BOARD_BootClockRUN().
The setting method is as follows.
void BOARD_SysPllConfigSpreadSpectrum()
{
const clock_sys_pll_config_t sysPllConfig_BOARD_BootClockRUN =
{
.loopDivider = 1, /* PLL loop divider, Fout = Fin * ( 20 + loopDivider*2 + numerator / denominator ) */
.numerator = 0, /* 30 bit numerator of fractional loop divider */
.denominator = 2400, /* 30 bit denominator of fractional loop divider */
.src=0, /* Bypass clock source, 0 - OSC 24M, 1 - CLK1_P and CLK1_N */
#if SPREAD_SPECTRUM_RANGE == SPREAD_RANGE_24M
.ss_enable = 1;
.ss_step = 6;
.ss_stop = 2400;
#elif SPREAD_SPECTRUM_RANGE == SPREAD_RANGE_12M
.ss_enable = 1;
.ss_step = 6;
.ss_stop = 1200;
#elif SPREAD_SPECTRUM_RANGE == SPREAD_RANGE_6M
.ss_enable = 1;
.ss_step = 6;
.ss_stop = 600;
#elif SPREAD_SPECTRUM_RANGE != NO_SPREAD_RANGE
#error SPREAD SPRECTRUM PARAMETER ERROR
#endif
};
CLOCK_InitSysPll(&sysPllConfig_BOARD_BootClockRUN);
}
int cpuInit(void)
{
BOARD_ConfigMPU();
BOARD_InitPins();
BOARD_BootClockRUN();
#if defined(__SPREAD_SPECTRUM__)
BOARD_SysPllConfigSpreadSpectrum();
#endif
BOARD_InitDebugConsole();
BOARD_InitModuleClock();
if (BOARD_InitSEMC() != kStatus_Success)
{
// PRINTF("\r\n SEMC SDRAM Init Failed\r\n");
return -1;
}
SysTick_Config(USEC_TO_COUNT(1000U, SYS_TICK_SOURCE_CLOCK));
return 0;
}
I set up the spread spectrum using only the formula below.
- Spectrum spread range = Fref * ss_stop/DENOM
- Modulation frequency = Fref * ss_step/(2*ss_stop)
I have a few questions here.
1) Is it correct to call BOARD_SysPllConfigSpreadSpectrum() after calling BOARD_BootClockRUN() as mentioned above?
There was no change at all, and when I searched the community, it said that it is usually done before sdram initialization, so I called it before BOARD_InitSEMC(). (cpuInit())
2) By adjusting the PLL loop divider (loopDivider) and numerator values, the Fout value becomes 528Mhz.
Is there no association between the Fout value and the SDRAM 200MHz clock?
What are the settings to apply 200Mhz spread spectrum?
Please let me know what I did wrong..
Regards,
