<avr/interrupt.h>: Interrupts(3)

NAME
<avr/interrupt.h>: Interrupts -

Detailed Description

Note:
    This discussion of interrupts was originally taken from Rich Neswold's document. See Acknowledgments.

  Introduction to avr-libc's interrupt handling

It's nearly impossible to find compilers that agree on how to handle interrupt code. Since the C language tries to stay away from machine dependent details, each compiler writer is forced to design their method of support.

In the AVR-GCC environment, the vector table is predefined to point to interrupt routines with predetermined names. By using the appropriate name, your routine will be called when the corresponding interrupt occurs. The device library provides a set of default interrupt routines, which will get used if you don't define your own.

Patching into the vector table is only one part of the problem. The compiler uses, by convention, a set of registers when it's normally executing compiler-generated code. It's important that these registers, as well as the status register, get saved and restored. The extra code needed to do this is enabled by tagging the interrupt function with __attribute__((signal)).

These details seem to make interrupt routines a little messy, but all these details are handled by the Interrupt API. An interrupt routine is defined with ISR(). This macro register and mark the routine as an interrupt handler for the specified peripheral. The following is an example definition of a handler for the ADC interrupt.

#include <avr/interrupt.h>
ISR(ADC_vect)
{
    // user code here
}

Refer to the chapter explaining assembler programming for an explanation about interrupt routines written solely in assembler language.

  Catch-all interrupt vector

If an unexpected interrupt occurs (interrupt is enabled and no handler is installed, which usually indicates a bug), then the default action is to reset the device by jumping to the reset vector. You can override this by supplying a function named BADISR_vect which should be defined with ISR() as such. (The name BADISR_vect is actually an alias for __vector_default. The latter must be used inside assembly code in case <avr/interrupt.h> is not included.)

#include <avr/interrupt.h>
ISR(BADISR_vect)
{
    // user code here
}

  Nested interrupts

The AVR hardware clears the global interrupt flag in SREG before entering an interrupt vector. Thus, normally interrupts will remain disabled inside the handler until the handler exits, where the RETI instruction (that is emitted by the compiler as part of the normal function epilogue for an interrupt handler) will eventually re-enable further interrupts. For that reason, interrupt handlers normally do not nest. For most interrupt handlers, this is the desired behaviour, for some it is even required in order to prevent infinitely recursive interrupts (like UART interrupts, or level-triggered external interrupts). In rare circumstances though it might be desired to re-enable the global interrupt flag as early as possible in the interrupt handler, in order to not defer any other interrupt more than absolutely needed. This could be done using an sei() instruction right at the beginning of the interrupt handler, but this still leaves few instructions inside the compiler-generated function prologue to run with global interrupts disabled. The compiler can be instructed to insert an SEI instruction right at the beginning of an interrupt handler by declaring the handler the following way:

ISR(XXX_vect, ISR_NOBLOCK)
{
  ...
}

where XXX_vect is the name of a valid interrupt vector for the MCU type in question, as explained below.

  Two vectors sharing the same code

In some circumstances, the actions to be taken upon two different interrupts might be completely identical so a single implementation for the ISR would suffice. For example, pin-change interrupts arriving from two different ports could logically signal an event that is independent from the actual port (and thus interrupt vector) where it happened. Sharing interrupt vector code can be accomplished using the ISR_ALIASOF() attribute to the ISR macro:

ISR(PCINT0_vect)
{
  ...
  // Code to handle the event.
}
ISR(PCINT1_vect, ISR_ALIASOF(PCINT0_vect));

Note:
    There is no body to the aliased ISR.

Note that the ISR_ALIASOF() feature requires GCC 4.2 or above (or a patched version of GCC 4.1.x). See the documentation of the ISR_ALIAS() macro for an implementation which is less elegant but could be applied to all compiler versions.

  Empty interrupt service routines

In rare circumstances, in interrupt vector does not need any code to be implemented at all. The vector must be declared anyway, so when the interrupt triggers it won't execute the BADISR_vect code (which by default restarts the application).

This could for example be the case for interrupts that are solely enabled for the purpose of getting the controller out of sleep_mode().

A handler for such an interrupt vector can be declared using the EMPTY_INTERRUPT() macro:

EMPTY_INTERRUPT(ADC_vect);

Note:
    There is no body to this macro.

  Manually defined ISRs

In some circumstances, the compiler-generated prologue and epilogue of the ISR might not be optimal for the job, and a manually defined ISR could be considered particularly to speedup the interrupt handling.

One solution to this could be to implement the entire ISR as manual assembly code in a separate (assembly) file. See Combining C and assembly source files for an example of how to implement it that way.

Another solution is to still implement the ISR in C language but take over the compiler's job of generating the prologue and epilogue. This can be done using the ISR_NAKED attribute to the ISR() macro. Note that the compiler does not generate anything as prologue or epilogue, so the final reti() must be provided by the actual implementation. SREG must be manually saved if the ISR code modifies it, and the compiler-implied assumption of __zero_reg__ always being 0 could be wrong (e. g. when interrupting right after of a MUL instruction).

ISR(TIMER1_OVF_vect, ISR_NAKED)
{
  PORTB |= _BV(0);  // results in SBI which does not affect SREG
  reti();
}

  Choosing the vector: Interrupt vector names

The interrupt is chosen by supplying one of the symbols in following table.

There are currently two different styles present for naming the vectors. One form uses names starting with SIG_, followed by a relatively verbose but arbitrarily chosen name describing the interrupt vector. This has been the only available style in avr-libc up to version 1.2.x.

Starting with avr-libc version 1.4.0, a second style of interrupt vector names has been added, where a short phrase for the vector description is followed by _vect. The short phrase matches the vector name as described in the datasheet of the respective device (and in Atmel's XML files), with spaces replaced by an underscore and other non-alphanumeric characters dropped. Using the suffix _vect is intented to improve portability to other C compilers available for the AVR that use a similar naming convention.

The historical naming style might become deprecated in a future release, so it is not recommended for new projects.

Note:
    The ISR() macro cannot really spell-check the argument passed to them. Thus, by misspelling one of the names below in a call to ISR(), a function will be created that, while possibly being usable as an interrupt function, is not actually wired into the interrupt vector table. The compiler will generate a warning if it detects a suspiciously looking name of a ISR() function (i.e. one that after macro replacement does not start with '__vector_').

  Vector name Old vector name Description Applicable for device

ADC_vect SIG_ADC ADC Conversion Complete AT90S2333, AT90S4433, AT90S4434, AT90S8535, AT90PWM3, AT90PWM2, AT90PWM1, AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega16, ATmega163, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8, ATmega8535, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATtiny13, ATtiny15, ATtiny26, ATtiny24, ATtiny44, ATtiny84, ATtiny45, ATtiny25, ATtiny85, ATtiny261, ATtiny461, ATtiny861, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 ANALOG_COMP_0_vect SIG_COMPARATOR0 Analog Comparator 0 AT90PWM3, AT90PWM2, AT90PWM1 ANALOG_COMP_1_vect SIG_COMPARATOR1 Analog Comparator 1 AT90PWM3, AT90PWM2, AT90PWM1 ANALOG_COMP_2_vect SIG_COMPARATOR2 Analog Comparator 2 AT90PWM3, AT90PWM2, AT90PWM1 ANALOG_COMP_vect SIG_COMPARATOR Analog Comparator AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 ANA_COMP_vect SIG_COMPARATOR Analog Comparator AT90S1200, AT90S2313, AT90S2333, AT90S4414, AT90S4433, AT90S4434, AT90S8515, AT90S8535, ATmega16, ATmega161, ATmega162, ATmega163, ATmega32, ATmega323, ATmega8, ATmega8515, ATmega8535, ATtiny11, ATtiny12, ATtiny13, ATtiny15, ATtiny2313, ATtiny26, ATtiny28, ATtiny24, ATtiny44, ATtiny84, ATtiny45, ATtiny25, ATtiny85, ATtiny261, ATtiny461, ATtiny861 CANIT_vect SIG_CAN_INTERRUPT1 CAN Transfer Complete or Error AT90CAN128, AT90CAN32, AT90CAN64 EEPROM_READY_vect SIG_EEPROM_READY, SIG_EE_READY ATtiny2313 EE_RDY_vect SIG_EEPROM_READY EEPROM Ready AT90S2333, AT90S4433, AT90S4434, AT90S8535, ATmega16, ATmega161, ATmega162, ATmega163, ATmega32, ATmega323, ATmega8, ATmega8515, ATmega8535, ATtiny12, ATtiny13, ATtiny15, ATtiny26, ATtiny24, ATtiny44, ATtiny84, ATtiny45, ATtiny25, ATtiny85, ATtiny261, ATtiny461, ATtiny861 EE_READY_vect SIG_EEPROM_READY EEPROM Ready AT90PWM3, AT90PWM2, AT90PWM1, AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega406, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 EXT_INT0_vect SIG_INTERRUPT0 External Interrupt Request 0 ATtiny24, ATtiny44, ATtiny84 INT0_vect SIG_INTERRUPT0 External Interrupt 0 AT90S1200, AT90S2313, AT90S2323, AT90S2333, AT90S2343, AT90S4414, AT90S4433, AT90S4434, AT90S8515, AT90S8535, AT90PWM3, AT90PWM2, AT90PWM1, AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega16, ATmega161, ATmega162, ATmega163, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega406, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8, ATmega8515, ATmega8535, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATtiny11, ATtiny12, ATtiny13, ATtiny15, ATtiny22, ATtiny2313, ATtiny26, ATtiny28, ATtiny45, ATtiny25, ATtiny85, ATtiny261, ATtiny461, ATtiny861, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 INT1_vect SIG_INTERRUPT1 External Interrupt Request 1 AT90S2313, AT90S2333, AT90S4414, AT90S4433, AT90S4434, AT90S8515, AT90S8535, AT90PWM3, AT90PWM2, AT90PWM1, AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega16, ATmega161, ATmega162, ATmega163, ATmega32, ATmega323, ATmega406, ATmega64, ATmega8, ATmega8515, ATmega8535, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATtiny2313, ATtiny28, ATtiny261, ATtiny461, ATtiny861, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 INT2_vect SIG_INTERRUPT2 External Interrupt Request 2 AT90PWM3, AT90PWM2, AT90PWM1, AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega16, ATmega161, ATmega162, ATmega32, ATmega323, ATmega406, ATmega64, ATmega8515, ATmega8535, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 INT3_vect SIG_INTERRUPT3 External Interrupt Request 3 AT90PWM3, AT90PWM2, AT90PWM1, AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega406, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 INT4_vect SIG_INTERRUPT4 External Interrupt Request 4 AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 INT5_vect SIG_INTERRUPT5 External Interrupt Request 5 AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 INT6_vect SIG_INTERRUPT6 External Interrupt Request 6 AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 INT7_vect SIG_INTERRUPT7 External Interrupt Request 7 AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 IO_PINS_vect SIG_PIN, SIG_PIN_CHANGE External Interrupt Request 0 ATtiny11, ATtiny12, ATtiny15, ATtiny26 LCD_vect SIG_LCD LCD Start of Frame ATmega169, ATmega169P, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega649, ATmega6490 LOWLEVEL_IO_PINS_vect SIG_PIN Low-level Input on Port B ATtiny28 OVRIT_vect SIG_CAN_OVERFLOW1 CAN Timer Overrun AT90CAN128, AT90CAN32, AT90CAN64 PCINT0_vect SIG_PIN_CHANGE0 Pin Change Interrupt Request 0 ATmega162, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega406, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATtiny13, ATtiny24, ATtiny44, ATtiny84, ATtiny45, ATtiny25, ATtiny85, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 PCINT1_vect SIG_PIN_CHANGE1 Pin Change Interrupt Request 1 ATmega162, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega406, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATtiny24, ATtiny44, ATtiny84, AT90USB162, AT90USB82 PCINT2_vect SIG_PIN_CHANGE2 Pin Change Interrupt Request 2 ATmega3250, ATmega3290, ATmega3290P, ATmega6450, ATmega6490, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644 PCINT3_vect SIG_PIN_CHANGE3 Pin Change Interrupt Request 3 ATmega3250, ATmega3290, ATmega3290P, ATmega6450, ATmega6490, ATmega324P, ATmega164P, ATmega644P, ATmega644 PCINT_vect SIG_PIN_CHANGE, SIG_PCINT ATtiny2313, ATtiny261, ATtiny461, ATtiny861 PSC0_CAPT_vect SIG_PSC0_CAPTURE PSC0 Capture Event AT90PWM3, AT90PWM2, AT90PWM1 PSC0_EC_vect SIG_PSC0_END_CYCLE PSC0 End Cycle AT90PWM3, AT90PWM2, AT90PWM1 PSC1_CAPT_vect SIG_PSC1_CAPTURE PSC1 Capture Event AT90PWM3, AT90PWM2, AT90PWM1 PSC1_EC_vect SIG_PSC1_END_CYCLE PSC1 End Cycle AT90PWM3, AT90PWM2, AT90PWM1 PSC2_CAPT_vect SIG_PSC2_CAPTURE PSC2 Capture Event AT90PWM3, AT90PWM2, AT90PWM1 PSC2_EC_vect SIG_PSC2_END_CYCLE PSC2 End Cycle AT90PWM3, AT90PWM2, AT90PWM1 SPI_STC_vect SIG_SPI Serial Transfer Complete AT90S2333, AT90S4414, AT90S4433, AT90S4434, AT90S8515, AT90S8535, AT90PWM3, AT90PWM2, AT90PWM1, AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega16, ATmega161, ATmega162, ATmega163, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8, ATmega8515, ATmega8535, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 SPM_RDY_vect SIG_SPM_READY Store Program Memory Ready ATmega16, ATmega162, ATmega32, ATmega323, ATmega8, ATmega8515, ATmega8535 SPM_READY_vect SIG_SPM_READY Store Program Memory Read AT90PWM3, AT90PWM2, AT90PWM1, AT90CAN128, AT90CAN32, AT90CAN64, ATmega128, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega406, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIM0_COMPA_vect SIG_OUTPUT_COMPARE0A Timer/Counter Compare Match A ATtiny13, ATtiny24, ATtiny44, ATtiny84, ATtiny45, ATtiny25, ATtiny85 TIM0_COMPB_vect SIG_OUTPUT_COMPARE0B Timer/Counter Compare Match B ATtiny13, ATtiny24, ATtiny44, ATtiny84, ATtiny45, ATtiny25, ATtiny85 TIM0_OVF_vect SIG_OVERFLOW0 Timer/Counter0 Overflow ATtiny13, ATtiny24, ATtiny44, ATtiny84, ATtiny45, ATtiny25, ATtiny85 TIM1_CAPT_vect SIG_INPUT_CAPTURE1 Timer/Counter1 Capture Event ATtiny24, ATtiny44, ATtiny84 TIM1_COMPA_vect SIG_OUTPUT_COMPARE1A Timer/Counter1 Compare Match A ATtiny24, ATtiny44, ATtiny84, ATtiny45, ATtiny25, ATtiny85 TIM1_COMPB_vect SIG_OUTPUT_COMPARE1B Timer/Counter1 Compare Match B ATtiny24, ATtiny44, ATtiny84, ATtiny45, ATtiny25, ATtiny85 TIM1_OVF_vect SIG_OVERFLOW1 Timer/Counter1 Overflow ATtiny24, ATtiny44, ATtiny84, ATtiny45, ATtiny25, ATtiny85 TIMER0_CAPT_vect SIG_INPUT_CAPTURE0 ADC Conversion Complete ATtiny261, ATtiny461, ATtiny861 TIMER0_COMPA_vect SIG_OUTPUT_COMPARE0A TimerCounter0 Compare Match A ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATtiny2313, ATtiny261, ATtiny461, ATtiny861, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER0_COMPB_vect SIG_OUTPUT_COMPARE0B, SIG_OUTPUT_COMPARE0_B Timer Counter 0 Compare Match B AT90PWM3, AT90PWM2, AT90PWM1, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATtiny2313, ATtiny261, ATtiny461, ATtiny861, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER0_COMP_A_vect SIG_OUTPUT_COMPARE0A, SIG_OUTPUT_COMPARE0_A Timer/Counter0 Compare Match A AT90PWM3, AT90PWM2, AT90PWM1 TIMER0_COMP_vect SIG_OUTPUT_COMPARE0 Timer/Counter0 Compare Match AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega16, ATmega161, ATmega162, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8515, ATmega8535 TIMER0_OVF0_vect SIG_OVERFLOW0 Timer/Counter0 Overflow AT90S2313, AT90S2323, AT90S2343, ATtiny22, ATtiny26 TIMER0_OVF_vect SIG_OVERFLOW0 Timer/Counter0 Overflow AT90S1200, AT90S2333, AT90S4414, AT90S4433, AT90S4434, AT90S8515, AT90S8535, AT90PWM3, AT90PWM2, AT90PWM1, AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega16, ATmega161, ATmega162, ATmega163, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8, ATmega8515, ATmega8535, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATtiny11, ATtiny12, ATtiny15, ATtiny2313, ATtiny28, ATtiny261, ATtiny461, ATtiny861, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER1_CAPT1_vect SIG_INPUT_CAPTURE1 Timer/Counter1 Capture Event AT90S2313 TIMER1_CAPT_vect SIG_INPUT_CAPTURE1 Timer/Counter Capture Event AT90S2333, AT90S4414, AT90S4433, AT90S4434, AT90S8515, AT90S8535, AT90PWM3, AT90PWM2, AT90PWM1, AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega16, ATmega161, ATmega162, ATmega163, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8, ATmega8515, ATmega8535, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATtiny2313, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER1_CMPA_vect SIG_OUTPUT_COMPARE1A Timer/Counter1 Compare Match 1A ATtiny26 TIMER1_CMPB_vect SIG_OUTPUT_COMPARE1B Timer/Counter1 Compare Match 1B ATtiny26 TIMER1_COMP1_vect SIG_OUTPUT_COMPARE1A Timer/Counter1 Compare Match AT90S2313 TIMER1_COMPA_vect SIG_OUTPUT_COMPARE1A Timer/Counter1 Compare Match A AT90S4414, AT90S4434, AT90S8515, AT90S8535, AT90PWM3, AT90PWM2, AT90PWM1, AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega16, ATmega161, ATmega162, ATmega163, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8, ATmega8515, ATmega8535, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATtiny2313, ATtiny261, ATtiny461, ATtiny861, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER1_COMPB_vect SIG_OUTPUT_COMPARE1B Timer/Counter1 Compare MatchB AT90S4414, AT90S4434, AT90S8515, AT90S8535, AT90PWM3, AT90PWM2, AT90PWM1, AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega16, ATmega161, ATmega162, ATmega163, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8, ATmega8515, ATmega8535, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATtiny2313, ATtiny261, ATtiny461, ATtiny861, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER1_COMPC_vect SIG_OUTPUT_COMPARE1C Timer/Counter1 Compare Match C AT90CAN128, AT90CAN32, AT90CAN64, ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER1_COMPD_vect SIG_OUTPUT_COMPARE0D Timer/Counter1 Compare Match D ATtiny261, ATtiny461, ATtiny861 TIMER1_COMP_vect SIG_OUTPUT_COMPARE1A Timer/Counter1 Compare Match AT90S2333, AT90S4433, ATtiny15 TIMER1_OVF1_vect SIG_OVERFLOW1 Timer/Counter1 Overflow AT90S2313, ATtiny26 TIMER1_OVF_vect SIG_OVERFLOW1 Timer/Counter1 Overflow AT90S2333, AT90S4414, AT90S4433, AT90S4434, AT90S8515, AT90S8535, AT90PWM3, AT90PWM2, AT90PWM1, AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega16, ATmega161, ATmega162, ATmega163, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8, ATmega8515, ATmega8535, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATtiny15, ATtiny2313, ATtiny261, ATtiny461, ATtiny861, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER2_COMPA_vect SIG_OUTPUT_COMPARE2A Timer/Counter2 Compare Match A ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER2_COMPB_vect SIG_OUTPUT_COMPARE2B Timer/Counter2 Compare Match A ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER2_COMP_vect SIG_OUTPUT_COMPARE2 Timer/Counter2 Compare Match AT90S4434, AT90S8535, AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega16, ATmega161, ATmega162, ATmega163, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8, ATmega8535 TIMER2_OVF_vect SIG_OVERFLOW2 Timer/Counter2 Overflow AT90S4434, AT90S8535, AT90CAN128, AT90CAN32, AT90CAN64, ATmega103, ATmega128, ATmega16, ATmega161, ATmega162, ATmega163, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega32, ATmega323, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega8, ATmega8535, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER3_CAPT_vect SIG_INPUT_CAPTURE3 Timer/Counter3 Capture Event AT90CAN128, AT90CAN32, AT90CAN64, ATmega128, ATmega162, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER3_COMPA_vect SIG_OUTPUT_COMPARE3A Timer/Counter3 Compare Match A AT90CAN128, AT90CAN32, AT90CAN64, ATmega128, ATmega162, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER3_COMPB_vect SIG_OUTPUT_COMPARE3B Timer/Counter3 Compare Match B AT90CAN128, AT90CAN32, AT90CAN64, ATmega128, ATmega162, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER3_COMPC_vect SIG_OUTPUT_COMPARE3C Timer/Counter3 Compare Match C AT90CAN128, AT90CAN32, AT90CAN64, ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER3_OVF_vect SIG_OVERFLOW3 Timer/Counter3 Overflow AT90CAN128, AT90CAN32, AT90CAN64, ATmega128, ATmega162, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TIMER4_CAPT_vect SIG_INPUT_CAPTURE4 Timer/Counter4 Capture Event ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 TIMER4_COMPA_vect SIG_OUTPUT_COMPARE4A Timer/Counter4 Compare Match A ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 TIMER4_COMPB_vect SIG_OUTPUT_COMPARE4B Timer/Counter4 Compare Match B ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 TIMER4_COMPC_vect SIG_OUTPUT_COMPARE4C Timer/Counter4 Compare Match C ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 TIMER4_OVF_vect SIG_OVERFLOW4 Timer/Counter4 Overflow ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 TIMER5_CAPT_vect SIG_INPUT_CAPTURE5 Timer/Counter5 Capture Event ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 TIMER5_COMPA_vect SIG_OUTPUT_COMPARE5A Timer/Counter5 Compare Match A ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 TIMER5_COMPB_vect SIG_OUTPUT_COMPARE5B Timer/Counter5 Compare Match B ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 TIMER5_COMPC_vect SIG_OUTPUT_COMPARE5C Timer/Counter5 Compare Match C ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 TIMER5_OVF_vect SIG_OVERFLOW5 Timer/Counter5 Overflow ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 TWI_vect SIG_2WIRE_SERIAL 2-wire Serial Interface AT90CAN128, AT90CAN32, AT90CAN64, ATmega128, ATmega16, ATmega163, ATmega32, ATmega323, ATmega406, ATmega64, ATmega8, ATmega8535, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 TXDONE_vect SIG_TXDONE Transmission Done, Bit Timer Flag 2 Interrupt AT86RF401 TXEMPTY_vect SIG_TXBE Transmit Buffer Empty, Bit Itmer Flag 0 Interrupt AT86RF401 UART0_RX_vect SIG_UART0_RECV UART0, Rx Complete ATmega161 UART0_TX_vect SIG_UART0_TRANS UART0, Tx Complete ATmega161 UART0_UDRE_vect SIG_UART0_DATA UART0 Data Register Empty ATmega161 UART1_RX_vect SIG_UART1_RECV UART1, Rx Complete ATmega161 UART1_TX_vect SIG_UART1_TRANS UART1, Tx Complete ATmega161 UART1_UDRE_vect SIG_UART1_DATA UART1 Data Register Empty ATmega161 UART_RX_vect SIG_UART_RECV UART, Rx Complete AT90S2313, AT90S2333, AT90S4414, AT90S4433, AT90S4434, AT90S8515, AT90S8535, ATmega103, ATmega163, ATmega8515 UART_TX_vect SIG_UART_TRANS UART, Tx Complete AT90S2313, AT90S2333, AT90S4414, AT90S4433, AT90S4434, AT90S8515, AT90S8535, ATmega103, ATmega163, ATmega8515 UART_UDRE_vect SIG_UART_DATA UART Data Register Empty AT90S2313, AT90S2333, AT90S4414, AT90S4433, AT90S4434, AT90S8515, AT90S8535, ATmega103, ATmega163, ATmega8515 USART0_RXC_vect SIG_USART0_RECV USART0, Rx Complete ATmega162 USART0_RX_vect SIG_UART0_RECV USART0, Rx Complete AT90CAN128, AT90CAN32, AT90CAN64, ATmega128, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega325, ATmega329, ATmega329P, ATmega64, ATmega645, ATmega649, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644 USART0_TXC_vect SIG_USART0_TRANS USART0, Tx Complete ATmega162 USART0_TX_vect SIG_UART0_TRANS USART0, Tx Complete AT90CAN128, AT90CAN32, AT90CAN64, ATmega128, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega64, ATmega645, ATmega6450, ATmega649, ATmega6490, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644 USART0_UDRE_vect SIG_UART0_DATA USART0 Data Register Empty AT90CAN128, AT90CAN32, AT90CAN64, ATmega128, ATmega162, ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega325, ATmega329, ATmega329P, ATmega64, ATmega645, ATmega649, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644 USART1_RXC_vect SIG_USART1_RECV USART1, Rx Complete ATmega162 USART1_RX_vect SIG_UART1_RECV USART1, Rx Complete AT90CAN128, AT90CAN32, AT90CAN64, ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 USART1_TXC_vect SIG_USART1_TRANS USART1, Tx Complete ATmega162 USART1_TX_vect SIG_UART1_TRANS USART1, Tx Complete AT90CAN128, AT90CAN32, AT90CAN64, ATmega128, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 USART1_UDRE_vect SIG_UART1_DATA USART1, Data Register Empty AT90CAN128, AT90CAN32, AT90CAN64, ATmega128, ATmega162, ATmega64, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646 USART2_RX_vect SIG_USART2_RECV USART2, Rx Complete ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 USART2_TX_vect SIG_USART2_TRANS USART2, Tx Complete ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 USART2_UDRE_vect SIG_USART2_DATA USART2 Data register Empty ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 USART3_RX_vect SIG_USART3_RECV USART3, Rx Complete ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 USART3_TX_vect SIG_USART3_TRANS USART3, Tx Complete ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 USART3_UDRE_vect SIG_USART3_DATA USART3 Data register Empty ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561 USART_RXC_vect SIG_USART_RECV, SIG_UART_RECV USART, Rx Complete ATmega16, ATmega32, ATmega323, ATmega8 USART_RX_vect SIG_USART_RECV, SIG_UART_RECV USART, Rx Complete AT90PWM3, AT90PWM2, AT90PWM1, ATmega3250, ATmega3290, ATmega3290P, ATmega6450, ATmega6490, ATmega8535, ATmega168, ATmega48, ATmega88, ATtiny2313 USART_TXC_vect SIG_USART_TRANS, SIG_UART_TRANS USART, Tx Complete ATmega16, ATmega32, ATmega323, ATmega8 USART_TX_vect SIG_USART_TRANS, SIG_UART_TRANS USART, Tx Complete AT90PWM3, AT90PWM2, AT90PWM1, ATmega8535, ATmega168, ATmega48, ATmega88, ATtiny2313 USART_UDRE_vect SIG_USART_DATA, SIG_UART_DATA USART Data Register Empty AT90PWM3, AT90PWM2, AT90PWM1, ATmega16, ATmega32, ATmega323, ATmega3250, ATmega3290, ATmega3290P, ATmega6450, ATmega6490, ATmega8, ATmega8535, ATmega168, ATmega48, ATmega88, ATtiny2313 USI_OVERFLOW_vect SIG_USI_OVERFLOW USI Overflow ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega645, ATmega6450, ATmega649, ATmega6490, ATtiny2313 USI_OVF_vect SIG_USI_OVERFLOW USI Overflow ATtiny26, ATtiny24, ATtiny44, ATtiny84, ATtiny45, ATtiny25, ATtiny85, ATtiny261, ATtiny461, ATtiny861 USI_START_vect SIG_USI_START USI Start Condition ATmega165, ATmega165P, ATmega169, ATmega169P, ATmega325, ATmega3250, ATmega329, ATmega329P, ATmega3290, ATmega3290P, ATmega645, ATmega6450, ATmega649, ATmega6490, ATtiny2313, ATtiny45, ATtiny25, ATtiny85, ATtiny261, ATtiny461, ATtiny861 USI_STRT_vect SIG_USI_START USI Start ATtiny26 USI_STR_vect SIG_USI_START USI START ATtiny24, ATtiny44, ATtiny84 WATCHDOG_vect SIG_WATCHDOG_TIMEOUT Watchdog Time-out ATtiny24, ATtiny44, ATtiny84 WDT_OVERFLOW_vect SIG_WATCHDOG_TIMEOUT, SIG_WDT_OVERFLOW Watchdog Timer Overflow ATtiny2313 WDT_vect SIG_WDT, SIG_WATCHDOG_TIMEOUT Watchdog Timeout Interrupt AT90PWM3, AT90PWM2, AT90PWM1, ATmega406, ATmega168, ATmega48, ATmega88, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, ATmega324P, ATmega164P, ATmega644P, ATmega644, ATtiny13, ATtiny45, ATtiny25, ATtiny85, ATtiny261, ATtiny461, ATtiny861, AT90USB162, AT90USB82, AT90USB1287, AT90USB1286, AT90USB647, AT90USB646

  Global manipulation of the interrupt flag
The global interrupt flag is maintained in the I bit of the status register (SREG).
#define sei()
#define cli()

  Macros for writing interrupt handler functions
#define ISR(vector, attributes)
#define SIGNAL(vector)
#define EMPTY_INTERRUPT(vector)
#define ISR_ALIAS(vector, target_vector)
#define reti()
#define BADISR_vect

  ISR attributes
#define ISR_BLOCK
#define ISR_NOBLOCK
#define ISR_NAKED
#define ISR_ALIASOF(target_vector)

Define Documentation

  #define BADISR_vect

 #include <avr/interrupt.h>

This is a vector which is aliased to __vector_default, the vector executed when an ISR fires with no accompanying ISR handler. This may be used along with the ISR() macro to create a catch-all for undefined but used ISRs for debugging purposes.

  #define cli()

 #include <avr/interrupt.h>

Disables all interrupts by clearing the global interrupt mask. This function actually compiles into a single line of assembly, so there is no function call overhead.

  #define EMPTY_INTERRUPT(vector)

 #include <avr/interrupt.h>

Defines an empty interrupt handler function. This will not generate any prolog or epilog code and will only return from the ISR. Do not define a function body as this will define it for you. Example:

 EMPTY_INTERRUPT(ADC_vect);

  #define ISR(vector, attributes)

 #include <avr/interrupt.h>

Introduces an interrupt handler function (interrupt service routine) that runs with global interrupts initially disabled by default with no attributes specified.

The attributes are optional and alter the behaviour and resultant generated code of the interrupt routine. Multiple attributes may be used for a single function, with a space seperating each attribute.

Valid attributes are ISR_BLOCK, ISR_NOBLOCK, ISR_NAKED and ISR_ALIASOF(vect).

vector must be one of the interrupt vector names that are valid for the particular MCU type.

  #define ISR_ALIAS(vector, target_vector)

 #include <avr/interrupt.h>

Aliases a given vector to another one in the same manner as the ISR_ALIASOF attribute for the ISR() macro. Unlike the ISR_ALIASOF attribute macro however, this is compatible for all versions of GCC rather than just GCC version 4.2 onwards.

Note:
    This macro creates a trampoline function for the aliased macro. This will result in a two cycle penalty for the aliased vector compared to the ISR the vector is aliased to, due to the JMP/RJMP opcode used.

Deprecated
    For new code, the use of ISR(..., ISR_ALIASOF(...)) is recommended.

Example:

    ISR(INT0_vect)
    {
        PORTB = 42;
    }
    ISR_ALIAS(INT1_vect, INT0_vect);

  #define ISR_ALIASOF(target_vector)

 #include <avr/interrupt.h>

The ISR is linked to another ISR, specified by the vect parameter. This is compatible with GCC 4.2 and greater only.

Use this attribute in the attributes parameter of the ISR macro.

  #define ISR_BLOCK

 # include <avr/interrupt.h>

Identical to an ISR with no attributes specified. Global interrupts are initially disabled by the AVR hardware when entering the ISR, without the compiler modifying this state.

Use this attribute in the attributes parameter of the ISR macro.

  #define ISR_NAKED

 # include <avr/interrupt.h>

ISR is created with no prologue or epilogue code. The user code is responsible for preservation of the machine state including the SREG register, as well as placing a reti() at the end of the interrupt routine.

Use this attribute in the attributes parameter of the ISR macro.

  #define ISR_NOBLOCK

 # include <avr/interrupt.h>

ISR runs with global interrupts initially enabled. The interrupt enable flag is activated by the compiler as early as possible within the ISR to ensure minimal processing delay for nested interrupts.

This may be used to create nested ISRs, however care should be taken to avoid stack overflows, or to avoid infinitely entering the ISR for those cases where the AVR hardware does not clear the respective interrupt flag before entering the ISR.

Use this attribute in the attributes parameter of the ISR macro.

  #define reti()

 #include <avr/interrupt.h>

Returns from an interrupt routine, enabling global interrupts. This should be the last command executed before leaving an ISR defined with the ISR_NAKED attribute.

This macro actually compiles into a single line of assembly, so there is no function call overhead.

  #define sei()

 #include <avr/interrupt.h>

Enables interrupts by setting the global interrupt mask. This function actually compiles into a single line of assembly, so there is no function call overhead.

  #define SIGNAL(vector)

 #include <avr/interrupt.h>

Introduces an interrupt handler function that runs with global interrupts initially disabled.

This is the same as the ISR macro without optional attributes.

Deprecated
    Do not use SIGNAL() in new code. Use ISR() instead.