PIC TIMER1 problem with internal low-power oscillator

[Brandon]

I'm trying to run a simple program on my PICKit 2 44-pin Demo Board
(PIC16F887) that keeps track of the overflows on TIMER1 when it is
clocked by the internal 32kHz crystal (see C code below for the CCS
complier). The problem I'm having is that I only seem to get two
TIMER1 interrupt overflows instead of one every two seconds like I
expect. Code works fine if I set up TIMER1 to run off the main
processor clock (8MHz).


#include <16F887.h>

#use delay(clock=8MHZ)

#FUSES
HS,INTRC,NOWDT,NOPUT,NOMCLR,NOPROTECT,NOCPD,NOBROWNOUT,NOIESO,NOFCMEN,NOLVP

int count; //keep track of TIMER1 overflows

#int_TIMER1
void TIMER1_isr(void)
{
count++; //increment count
output_d(count); //display count on LEDs
}

void main()
{
setup_timer_1(T1_EXTERNAL|T1_CLK_OUT); //use low power 32kHz crystal
(i.e. T1CON=0x8F)
enable_interrupts(INT_TIMER1);
enable_interrupts(global);
count=0xFF; // turn on all LEDs to start
output_d(count);
while(1);
}

 

[donald]

I'm trying to run a simple program on my PICKit 2 44-pin Demo Board
(PIC16F887) that keeps track of the overflows on TIMER1 when it is
clocked by the internal 32kHz crystal (see C code below for the CCS
complier). The problem I'm having is that I only seem to get two
TIMER1 interrupt overflows instead of one every two seconds like I
expect. Code works fine if I set up TIMER1 to run off the main
processor clock (8MHz).


#include <16F887.h>

#use delay(clock=8MHZ)

#FUSES
HS,INTRC,NOWDT,NOPUT,NOMCLR,NOPROTECT,NOCPD,NOBROWNOUT,NOIESO,NOFCMEN,NOLVP

int count; //keep track of TIMER1 overflows

#int_TIMER1
void TIMER1_isr(void)
{
count++; //increment count
output_d(count); //display count on LEDs
}

void main()
{
setup_timer_1(T1_EXTERNAL|T1_CLK_OUT); //use low power 32kHz crystal
(i.e. T1CON=0x8F)
enable_interrupts(INT_TIMER1);
enable_interrupts(global);
count=0xFF; // turn on all LEDs to start
output_d(count);
while(1);
}

Check your #FUSES statement.

donald