Help Me Please!

[nxpxhy13]

My program in my circuit board, can work normally for a period of time, after a period of time, my PLL circuit damage, I will phase-locked loop initialization program shielding, the program can run, please give me some help. If you don't use PLL frequency multiplier circuit, how many MHz is the maximum frequency of external crystal oscillator? My CPU is mc9s12xe series.

[nxpxhy13]

Thank you very much. It's very helpful to me!

One more question, why should refdv be assigned first? I assign value to synr first, CPU can also work normally!

[lama · Accepted solution]

Hi

What could be wrong:

1) You use canned oscillator (external clock) with wrong output voltage. It must have Vddpll value of 1.8V. If it is larger the divider must be used.
Check the design with:
https://community.nxp.com/t5/S12-MagniV-Microcontrollers/Reference-schematics-for-S12-X-devices/ta-p...

This is ticking time bomb because of electromigration in oscillator circuitry.

2) Maximum oscillator value is defined in the Table A-24
a) Crystal oscillator range (loop controlled Pierce) fOSC 4.0 — 16 MHz
b) Full swing Pierce oscillator/external clock mode is selected fOSC 2.0 — 40 MHz

3) Incorrect order in PLL initialization. Refdv (divider) must be set earlier than Synr (multiplier).

void PLL_setup(unsigned char _synr, unsigned char _refdv, unsigned char _postdiv)
{
PLLCTL = 0B00000001; // CME=0,PLLON=0,FM1=0,FM2=0,FSTWKP=0,PRE=0,PCE=0,SCME=1
CLKSEL = 0B00000011; // PLLSEL=0,PSTP=0,PLLWAI=0,RTIWAI=1,COPWAI=1
REFDV = _refdv; // Set the divider register
SYNR = _synr; // Set the multiplier register
POSTDIV = _postdiv; // Set the post divider register
PLLCTL_PLLON = 1; // Enable the Phase Lock Loop
while(!CRGFLG_LOCK); // Wait till the PLL VCO is within tolerance
CLKSEL_PLLSEL = 1; // Select clock source from PLLCLK

// optional to be able to check correct bus clock
ECLKCTL_NECLK=0; // Enable the BusClk output at ECLK pin to see busclk if necessary
}

4) Incorrect design of oscillator circuitry and load capacitors.
(no wire, no plain under oscillator circuitry is allowed..it changes capacitance)

5) Incorrect registers calculation. Use calculator
https://www.nxp.com/docs/en/user-guide/S12XEIPLLCUG.pdf
https://www.nxp.com/downloads/en/calculators/S12XESW.zip

Best regards,

Ladislav