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Hot!Timer1 on PIC24FJ128GA010

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2019/11/20 09:14:20 (permalink)

Timer1 on PIC24FJ128GA010

I am working to configure the clock on the PIC24FJ128GA010.  To confirm oscillator and timer functionality, I am using an LED blinker to confirm delays.  I would like to use the internal oscillator / PLL combination to achieve 32 MHZ oscillation frequency.  When I configure the oscillator, I select 'FRCDIV' to select the fast RC oscillator with PLL module.  This would give me a FCYC = Fosc / 2.
Configuration bits are shown in the code snippet:
#pragma config POSCMOD = NONE // Primary Oscillator Select (Primary oscillator disabled)
#pragma config OSCIOFNC = OFF // Primary Oscillator Output Function (OSC2/CLKO/RC15 functions as CLKO (FOSC/2))
#pragma config FCKSM = CSDCMD // Clock Switching and Monitor (Clock switching and Fail-Safe Clock Monitor are disabled)
#pragma config FNOSC = FRCDIV // Oscillator Select (Fast RC Oscillator with PLL modjkule (FRCPLL))
#pragma config IESO = ON // Internal External Switch Over Mode (IESO mode (Two-Speed Start-up) enabled)

#pragma config WDTPS = PS32768 // Watchdog Timer Postscaler (1:32,768)
#pragma config FWPSA = PR128 // WDT Prescaler (Prescaler ratio of 1:128)
#pragma config WINDIS = OFF // Watchdog Timer Window (Windowed Watchdog Timer enabled; FWDTEN must be 1)
#pragma config FWDTEN = OFF // Watchdog Timer Enable (Watchdog Timer is disabled)
#pragma config ICS = PGx2 // Comm Channel Select (Emulator/debugger uses EMUC2/EMUD2)
#pragma config GWRP = OFF // General Code Segment Write Protect (Writes to program memory are allowed)
#pragma config GCP = OFF // General Code Segment Code Protect (Code protection is disabled)
#pragma config JTAGEN = OFF // JTAG Port Enable (JTAG port is disabled)

I then move on to configure the timer 1 register.  I do not intend to use the period reset so I do not initialize the PR1 register.  My initialization of timer 1 along with the delay function is shown below:
void initTimer(void)
    TMR1 = 0; /* Clear timer register */
    T1CON = 0x8030;

void Delay(void)
    while (TMR1 < Delay)
        if (TMR1 > 800)

What I am finding is that TMR1 is not incrementing above 900.  I wanted to see if I would be able to achieve a delay of 1 second but this would require TMR1 to count to ~62,500.  Since TMR1 is a 16 bit register this should be achievable?  Is there anything in my configuration that would be off?  I am using (2/32000000)*256*62500 = 1s.

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    Super Member
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    Re: Timer1 on PIC24FJ128GA010 2019/11/20 12:22:00 (permalink)
    What I am finding is that TMR1 is not incrementing above 900.

    How do you know?
    i.e. what precise test are you doing to determine this?

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