[SOLVED] problem with internal oscillator. PIC30f5011

[Raady Here]

Hi,

I have been working with the internal oscillator of PIC30F5011, and I followed these steps for calculation of timer

/****************************************************************************************
* Timer Delay Calculations used:
* 1. Crystal Source Frequency Fosc
* 2. Timer Frequency Ftimer = Fosc / 4
* 3. Using a Prescalar 1:8, then
* Ftimerpre = Ftimer / scalar value
* 4. Time Interval Ttimer = 1/Ftimerpre
* 5. To calculate the value to be filled in Timer rolling over
* register to generate 10m sec delay :
* No of count for 10 msec delay = 10 ms / Ttimer
****************************************************************************************/

so my calculations
for delay timer with no PLL is 2303 , PLL 4 is 9212.5 ~ 9213, PLL 8 is 18424

when ever I load PR value as 2303 the timer is working fine, and remaining rest it doesn't.
From this i knew despite the PLL that i apply i needed to load the calculations that made for PLL.

The thing I couldn't understand is when ever I am using an external oscillator (8MHz) it all working fine (for the calculations made fosc multiplied by pll), should I not apply PLL multiplied to Fosc while I am using internal oscillator ?




Here is the piece of code timer code I used

void INIT_TIMER(void)
{
	TRISGbits.TRISG12 = 0; 				// setting MCLR LED as output port
	LATGbits.LATG12   = 1; 				// setting on MCLR LED. 
	
	T1CON		= 0; 					// Disable Timer and reset
	TMR1 		= 0x0000; 				// Clear timer register
	PR1 			= _T1_TIME; 			// Load the Period Value of 10m sec.
									// _T1_TIME = 2303 made from calculations.

	IPC0bits.T1IP	= 7;					// set timer 1 interrupt priority level.
	IFS0bits.T1IF	= 0;					// Clear Timer1 Interrupt Flag
	IEC0bits.T1IE	= 1;					// Enable Timer1 interrupt
	
	T1CONbits.TCKPS = 0b01; 				// Select 1:8 Prescaler	
	T1CONbits.TCS 	= 0;					// Enable Internal clock (FOSC/4)
	T1CONbits.TON	= 1;					// Start Timer
}

Regards,
Raady

 

[nick703]

when u using internal oscillator " FAST RC OSCILLATOR (FRC) " that time PLL is apply but onther config setting like internal
" LOW POWER RC OSCILLATOR (LPRC) " u not apply PLL of internal Oscillator . and also try to disable WDT .

 

[Raady Here]

Hi nick,

Here I am attaching a short view of the configurations that I have made (where in I have chose Internal oscillator FRC and disabled watchdog).
If you are looking at the attachment, I have no option to work with FRC with no PLL, but I need to make calculations based on FRC no PLL irrespetive of my selection FRC 4PLL, FRC 8PLL, FRC 16PLL.

I have raised this question as this have applied the same to UART functionality(changing PLL didn't match UART register to print correctly).
Further I need to work on ADC where I have to take calculations similarly based on Fosc.

is there any changes that I need make ?

//************************SYSTEM CONFIGURATION BITS*************************************
_FOSC(CSW_FSCM_OFF & FRC_PLL4);	//Internal fast RC oecillator
_FWDT(WDT_OFF);				//Disable the watcdog timer
_FBORPOR(MCLR_EN & PWRT_OFF); 	//Enable the master clear pin
_FGS(CODE_PROT_OFF); 			// Disable code protection