PIC18F and CLKO on RA6: Output not working

[smoothVTer]

Hello,

Device:  PIC18F46J50 http://ww1.microchip.com/downloads/en/DeviceDoc/39931b.pdf

I'm using the Explorer 8 Discovery development board from Microchip, as well as the PIC18F46J50 plug-in module.   So far, everything has been working as expected.

I am interested in using the oscillator mode as described in this datasheet,  INTOSCPLLO   When this mode is chosen, the instruction clock is supposed to be output on pin RA6:





I am seeing no clock output at all from pin RA6 on the scope.   

What am I doing wrong?   Below is my code:

Code: [Select]

#include <xc.h>

// CONFIG2L
#pragma config OSC = INTOSCPLLO      // Oscillator (INTOSCPLLO (CLKO-RA6))
#pragma config T1DIG = OFF                 // T1OSCEN Enforcement (Secondary Oscillator clock source may not be selected)
#pragma config LPT1OSC = OFF             // Low-Power Timer1 Oscillator (High-power operation)
#pragma config FCMEN = OFF                // Fail-Safe Clock Monitor (Disabled)
#pragma config IESO = OFF                   // Internal External Oscillator Switch Over Mode (Disabled)


#BYTE REFOCON = getenv("SFR:REFOCON") // More portable;  show in Window->PIC memory views->SFR
#BIT   RODIV0  = REFOCON.0
#BIT   RODIV1 = REFOCON.1
#BIT   RODIV2 = REFOCON.2
#BIT   RODIV3 = REFOCON.3
#BIT   ROSEL  = REFOCON.4
#BIT   ROSSLP = REFOCON.5
#BIT   ROON   = REFOCON.7



void main(void)
{
    ROSEL = 0;                       // Use system clock as the base clock
    ROON  = 1;                       // Turn on reference clock output on RB2;  debugging to check if REFO = 8MHz;  it is
    TRISA = 0b00000000;     // Make sure RA6 is set as an output
    TRISB = 0b00000000;     // Make sure RB2 is set as an output
    while(1)
    {
         //nop here, nothing to do, just checking clock setups
    }
   
    return;
}





[voltsandjolts]

See Note 1 at the bottom of the picture you supplied. Maybe:

OSCTUNEbits.PLLEN = 1;

[smoothVTer]

After setting this up correctly, still no output on RA6   for the CLKO ( RA6 ) pin. 

Ooops, yes, I must set PLLEN = 1 in order to enable the PLL.   That bit was missing from my code above, as well as the PLLDIV setting, which must be divide-by-2 in order to get a 4MHz input into the PLL. 



RA6 does not seem to be a PPS pin so I am still unclear as to why there is no CLKO output.   

[taustin]

Is this working for you yet?

If the pin is also a shared analog input, try explicitly turning off the analog input. This has caught me and the students I work with many times. Analog input is turned on by default and even the most simple output test won't work.

Good Luck!