Datasheet

58
ATmega169A/PA/329A/PA/649A/P/3290A/PA/6490A/P [DATASHEET]
8284E–AVR–02/2013
0x3831/0x7831 out SPL,r16
0x3832/0x7832 sei ; Enable interrupts
0x3833/0x7833 <instr> xxx
12.2.1 Moving interrupts between application and boot space
he General Interrupt Control Register controls the placement of the Interrupt Vector table, see ”MCUCR – MCU
Control Register” on page 59.
To avoid unintentional changes of Interrupt Vector tables, a special write procedure must be followed to change the
IVSEL bit:
a. Write the Interrupt Vector Change Enable (IVCE) bit to one.
b. Within four cycles, write the desired value to IVSEL while writing a zero to IVCE.
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, inter-
rupts 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 dis-
abled 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 the sec-
tion
”Boot Loader Support – Read-While-Write Self-Programming” on page 278 for details on Boot Lock bits.
The following example shows how interrupts are moved.
Assembly code example
Move_interrupts:
;Get MCUCR
in r16, MCUCR
mov r17, r16
; Enable change of Interrupt Vectors
ori r16, (1<<IVCE)
out MCUCR, r16
; Move interrupts to Boot Flash section
ori r17, (1<<IVSEL)
out MCUCR, r17
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);
}