1.25.11 1.26.10 1.27.12 1.28.14 Periodic Interval Timer (PIT)
The Periodic Interval Timer (PIT) provides the operating system’s scheduler interrupt. It is designed to offer maximum accuracy and efficient management, even for systems with long response time.
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20-bit Programmable Counter plus 12-bit Interval Counter
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Reset-on-read Feature
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Both Counters Work on Master Clock/16
Using The Library
PIT peripheral library can be used to poll for a periodic timeout, generate periodic interrupts or generate timed waits. The following examples shows different modes of its usage.
Polling method
int main ( void ) { int i; /* Initialize all modules */ SYS_Initialize ( NULL ); while ( true ) { for (i=0; i<10; i++) { while(!PIT_TimerPeriodHasExpired()); PIT_TimerRestart(); } LED_BLUE_Toggle(); /* Maintain state machines of all polled MPLAB Harmony modules. */ SYS_Tasks ( ); } /* Execution should not come here during normal operation */ return ( EXIT_FAILURE ); }
Interrupt Method
static void pit_callback(uintptr_t context)
{
(void)context;
LED_BLUE_Toggle();
}
int main ( void )
{
/* Initialize all modules */
SYS_Initialize ( NULL );
PIT_TimerCallbackSet(pit_callback, NULL);
PIT_TimerStart();
while ( true )
{
/* Maintain state machines of all polled MPLAB Harmony modules. */
SYS_Tasks ( );
}
/* Execution should not come here during normal operation */
return ( EXIT_FAILURE );
}
Delay routines
int main ( void )
{
/* Initialize all modules */
SYS_Initialize ( NULL );
PIT_TimerCallbackSet(pit_callback, NULL);
PIT_TimerStart();
while ( true )
{
PIT_DelayMs(1000U);
LED_BLUE_Toggle();
/* Maintain state machines of all polled MPLAB Harmony modules. */
SYS_Tasks ( );
}
/* Execution should not come here during normal operation */
return ( EXIT_FAILURE );
}
Library Interface
Periodic Interval Timer peripheral library provides the following interfaces:
Functions
Name | Description |
---|---|
PIT_TimerInitialize | Initialize PIT registers per user configuration |
PIT_TimerRestart | Restart the PIT counter |
PIT_TimerStart | Start the PIT counter |
PIT_TimerStop | Stop the PIT counter |
PIT_TimerPeriodSet | Set the timer period value |
PIT_TimerPeriodGet | Get the timer period value |
PIT_TimerCounterGet | Get the timer counter value |
PIT_TimerCompareSet | Set the timer comparison value |
PIT_TimerFrequencyGet | Get the timer clock frequency |
PIT_TimerPeriodHasExpired | Return whether or not the Timer Period has expired |
PIT_DelayMs | Delays processing for x milliseconds |
PIT_DelayUs | Delays processing for x microseconds |
PIT_TimerCallbackSet | Register callback for PIT interrupt |
PIT_ClearInterrupt | PIT Clear Interrupt |
Data types and constants
Name | Type | Description |
---|---|---|
PIT_CALLBACK | Typedef | PIT Interrupt Callback Function definition |