1.8.18 1.25.18 1.26.16 1.28.21 1.34.17 1.35.12 1.36.15 1.41.18 1.42.16 Real-time Timer (RTT)
The RTT is built around a 32-bit counter used to count roll-over events of the programmable 16-bit prescaler driven from the 32-kHz slow clock source.
The RTT can also be configured to be driven by the 1Hz RTC signal, thus taking advantage of a calibrated 1Hz clock.
Using The Library
The RTT peripheral generates a periodic interrupt and/or triggers an alarm on a programmed value.
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Periodic interrupt is generated when the prescaler roll over generates the clock to increment real-time timer counter
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Alarm interrupt is generated when the time value matches the programmed alarm value The RTT continues to run in the device's low-power sleep modes, and it can be used as a source to wake up the system using the alarm function.
Periodic Interrupt
This example below demonstrates how to use RTT for periodic interrupt generation.
void Timeout_Handler (RTT_INTERRUPT_TYPE type, uintptr_t context) { if(type == RTT_PERIODIC) { LED_Toggle(); } } int main ( void ) { /* Register Callback */ RTT0_CallbackRegister(Timeout_Handler, (uintptr_t) NULL); /* Enable RTT */ RTT0_Enable(); while ( true ) { } }
The below example demonstrates how to set alarm and watch it being triggered when the timer reaches the corresponding value.
void Timeout_Handler (RTT_INTERRUPT_TYPE type, uintptr_t context)
{
if(type == RTT_ALARM)
{
// Alarm has occurred
}
}
int main ( void )
{
/* Register Callback */
RTT0_CallbackRegister(Timeout_Handler, (uintptr_t) NULL);
/* Set Alarm Value */
RTT_AlarmValueSet(10);
/* Enable RTT */
RTT0_Enable();
while ( true )
{
}
}
Library Interface
Real-time Timer peripheral library provides the following interfaces:
Functions
Name | Description |
---|---|
RTT_Initialize | Initialize the RTT peripheral |
RTT_Enable | Enables the Real Time Timer |
RTT_Disable | Disables the real Time Timer |
RTT_PrescalarUpdate | Updates the prescalar for the RTT peripheral |
RTT_AlarmValueSet | Sets the Alarm value for the RTT peripheral |
RTT_EnableInterrupt | Enable RTT interrupts |
RTT_DisableInterrupt | Disable RTT interrupts |
RTT_TimerValueGet | Returns the current timer value |
RTT_FrequencyGet | Returns the current RTT frequency |
RTT_CallbackRegister | Sets the pointer to the function (and it's context) to be called |
Data types and constants
Name | Type | Description |
---|---|---|
RTT_INTERRUPT_TYPE | Enum | Defines the data type for the RTT INTERRUPT TYPE |
RTT_CALLBACK | Typedef | Defines the data type and function signature for the RTT peripheral callback function |
RTT_OBJECT | Struct | Defines the data type for the RTT OBJECT |