Datasheet

ATtiny828 [DATASHEET]

8371A–AVR–08/12

When using the CLI instruction to disable interrupts, the interrupts will be immediately disabled. No interrupt will be

executed after the CLI instruction, even if it occurs simultaneously with the CLI instruction. The following example shows

how this can be used to avoid interrupts during the timed EEPROM write sequence.

Note: See “Code Examples” on page 7.

When using the SEI instruction to enable interrupts, the instruction following SEI will be executed before any pending

interrupts, as shown in the following example.

Note: See “Code Examples” on page 7.

4.7.1 Interrupt Response Time

The interrupt execution response for all the enabled AVR interrupts is four clock cycles minimum. After four clock cycles

the Program Vector address for the actual interrupt handling routine is executed. During this four clock cycle period, the

Program Counter is pushed onto the Stack. The vector is normally a jump to the interrupt routine, and this jump takes

three clock cycles. If an interrupt occurs during execution of a multi-cycle instruction, this instruction is completed before

the interrupt is served. If an interrupt occurs when the MCU is in sleep mode, the interrupt execution response time is

increased by four clock cycles. This increase comes in addition to the start-up time from the selected sleep mode.

Assembly Code Example

in r16, SREG ; store SREG value

cli ; disable interrupts during timed sequence

sbi EECR, EEMPE ; start EEPROM write

sbi EECR, EEPE

out SREG, r16 ; restore SREG value (I-bit)

C Code Example

char cSREG;

cSREG = SREG; /* store SREG value */

_CLI(); /* disable interrupts during timed sequence */

EECR |= (1<<EEMPE); /* start EEPROM write */

EECR |= (1<<EEPE);

SREG = cSREG; /* restore SREG value (I-bit) */

Assembly Code Example

sei ; set Global Interrupt Enable

sleep ; enter sleep, waiting for interrupt

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

C Code Example

_SEI(); /* set Global Interrupt Enable */

_SLEEP(); /* enter sleep, waiting for interrupt */

/* note: will enter sleep before any pending interrupt */