
60
8018P–AVR–08/10
ATmega169P
11.2.1
MCUCR – MCU Control Register
Bit 1 – IVSEL: Interrupt Vector Select
When the IVSEL bit is cleared (zero), the Interrupt Vectors are placed at the start of the Flash
memory. When this bit is set (one), the Interrupt Vectors are moved to the beginning of the Boot
Loader section of the Flash. The actual address of the start of the Boot Flash Section is deter-
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
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)
{
uchar temp;
/* Get MCUCR*/
temp = MCUCR;
/* Enable change of Interrupt Vectors */
MCUCR = temp | (1<<IVCE);
/* Move interrupts to Boot Flash section
*/ MCUCR = temp | (1<<IVSEL);
}
Bit
7
6
543210
0x35 (0x55)
JTD
-
PUD
–
IVSEL
IVCE
MCUCR
Read/Write
R/W
R
R/W
R
R/W
Initial Value
0
000000