Datasheet

ATmega48/88/168 Automotive [DATASHEET]
7530K–AVR–07/14
56
Interrupts will automatically be disabled while this sequence is executed. Interrupts are disabled in the cycle IVCE is set, and
they remain disabled until after the instruction following the write to IVSEL. If IVSEL is not written, interrupts remain disabled
for four cycles. The I-bit in the status register is unaffected by the automatic disabling.
Note: If interrupt vectors are placed in the boot loader section and boot lock bit BLB02 is programmed, interrupts are
disabled while executing from the Application section. If Interrupt Vectors are placed in the Application section
and boot lock bit BLB12 is programed, interrupts are disabled while executing from the boot loader section.
Refer to Section 24. “Boot Loader Support – Read-While-Write Self-Programming, ATmega88 and
ATmega168” on page 229 for details on boot lock bits.
This bit is not available in Atmel
®
ATmega48.
• Bit 0 – IVCE: Interrupt Vector Change Enable
The IVCE bit must be written to logic one to enable change of the IVSEL bit. IVCE is cleared by hardware four cycles after it
is written or when IVSEL is written. Setting the IVCE bit will disable interrupts, as explained in the IVSEL description above.
See code example below.
This bit is not available in Atmel ATmega48.
Assembly Code Example
Move_interrupts:
; Enable change of Interrupt Vectors
ldi r16, (1<<IVCE)
out MCUCR, r16
; Move interrupts to Boot Flash section
ldi r16, (1<<IVSEL)
out MCUCR, r16
ret
C Code Example
void Move_interrupts(void)
{
/* Enable change of Interrupt Vectors */
MCUCR = (1<<IVCE);
/* Move interrupts to Boot Flash section */
MCUCR = (1<<IVSEL);
}