Rainbow-electronics ATmega8515L Manuale Utente Scaricare il pdf (Pagina 13)

ATmega8515(L)

2512A–AVR–04/02

When using the SEI instruction to enableinterrupts, theinstruction following SEI will be

executedbeforeanypending interrupts, asshowninthis example.

Interrupt Response Time Theinterruptexecution response for all theenabled AVR interrupts isfourclock cycles

minimum. Afterfourclock cycles theProgram Vector address for theactual interrupt

handling routine is executed. During thisfourclock cycle period, theProgram Counter is

pushed onto the Stack.TheVector is normally a jump to theinterrupt routine, and this

jump takes three clock cycles. If an interruptoccurs during execution of amulti-cycle

instruction, this instruction iscompletedbeforetheinterruptisserved. If an interrupt

occurs when the MCU is in sleep mode, theinterruptexecution responsetimeis

increasedbyfourclock cycles.This increase comes in addition to the start-up time from

the selectedsleep mode.

A return from an interrupt handling routine takesfourclock cycles. During these four

clock cycles, theProgram Counter(two bytes) ispoppedback from the Stack, the Stack

Pointer is incrementedbytwo, and the I-bit in SREG isset.

Assembly Code Example

sei

; set global interrupt enable

sleep

; enter sleep, waiting for interrupt

; note: will enter sleep before any pending

; interrupt(s)

CCode Example

_SEI();

/* set global interrupt enable */

_SLEEP();

/* enter sleep, waiting for interrupt */

/* note: will enter sleep before any pending interrupt(s) */

1 2 ... 8 9 10 11 12 13 14 15 16 17 18 ... 222 223

Nessun commento

Rainbow-electronics ATmega8515L Manuale Utente Pagina 13