32 Mhz clock pulse outut from pic24f16ka102

[skbohra]

32 Mhz clock pulse output from pic24f16ka102

I am simply trying to get clock pulse output at CLKO(RA3) from pic24f16ka102 and according to the datasheet, following code should work, but I am not getting any pulse near 32Mhz, I am only getting random pulse with max frequency of some hundred Khz

#include "p24Fxxxx.h"

_FWDT	(FWDTEN_OFF);
_FOSCSEL(FNOSC_FRCPLL);
_FOSC(FCKSM_CSECMD & POSCFREQ_MS & OSCIOFNC_ON & POSCMOD_NONE)

int main(void)
{

// Use Internal 8 MHz Clock
OSCCON = 0x0000;
CLKDIV = 0x0000;
return 0;
}

 

[keith1200rs]

I may be wrong, but I am not sure you can use CLKO in FRCPLL mode:

OSCIOFNC:
1 = CLKO output signal active on the OSCO pin; primary oscillator must be disabled or configured for
the External Clock mode (EC) for the CLKO to be active (POSCMD<1:0> = 11 or 00)

You might be able to use REFO instead, although it would be on a different pin

Keith.

 

[skbohra]

I may be wrong, but I am not sure you can use CLKO in FRCPLL mode:



You might be able to use REFO instead, although it would be on a different pin

Keith.

I have tried without PLL mode but still I am not able to get any values more than couple of hundred KHz, my main objective is to generate a square wave of frequency in 500KHz to 1MHz, I have tried the Output compare module as well but the maximum frequency I get is 62KHz, following is the code for square wave using Output Compare module

#include "p24Fxxxx.h"

_FWDT	(FWDTEN_OFF);
_FOSCSEL(FNOSC_FRCPLL);
_FOSC(FCKSM_CSECMD & POSCFREQ_MS & OSCIOFNC_OFF & POSCMOD_NONE)

int main(void)
{

// Use Internal 8 MHz Clock
OSCCON = 0x0000;
CLKDIV = 0x0000;
REFOCON = 0x8000;

 T2CON = 0x00; //Stops the Timer2 and reset control reg.
    TMR2 = 0x00; //Clear contents of the timer register4
    T2CONbits.TCKPS = 0b10; // 1:64 prescale
    T2CONbits.TCS = 0;      // internal clock source
    IPC1bits.T2IP = 0x01; //Setup Timer1 interrupt for desired priority
    IEC0bits.T2IE = 1; //enable interrupts for timer2
    T2CONbits.TON = 1;

    OC1CONbits.OCTSEL = 0; //use timer 2
    OC1CONbits.OCM = 0b101; //single output pulse generation mode
    OC1CONbits.OCSIDL = 0; //continue in idle mode
    IEC0bits.OC1IE = 0;
    OC1RS=2;
    OC1R=1; // first match
    PR2 = 3;
    
while(1){
    
}
return 0;
}

void __attribute__((__interrupt__)) _OC1Interrupt( void )
{

/* Interrupt Service Routine code goes here */
IFS0bits.OC1IF = 0; // Clear OC1 interrupt flag
//OC1CONbits.OCM = 0b100; //single output pulse generation mode
//T2CON = 0x00;
}

 

[keith1200rs]

I have tried without PLL mode but still I am not able to get any values more than couple of hundred KHz, my main objective is to generate a square wave of frequency in 500KHz to 1MHz, I have tried the Output compare module as well but the maximum frequency I get is 62KHz, following is the code for square wave using Output Compare module

It is not the PLL that causes the problem - it needs to be EC mode.

You should be able to generate 500kHz to 1MHz with no problem as long as you have a reasonable clock speed. I normally use the 24H and 24E and can generate 35MHz from TIMER1/OC1 with the 24E.

Your code uses 1:64 prescale so with 8MHz clock you are therefore running at 125kHz. Try 1:1 for the prescaler. If you want it to free-run you shouldn't need to use the interrupt.

Keith