Datasheet

60
8284D–AVR–6/11
ATmega169A/PA/329A/PA/3290A/PA/649A/P/6490A/P
12.3 Register Description
12.3.1 MCUCR – MCU Control Register
Note: 1. Only available in the picoPower devices ATmega169PA/329PA/3290PA/649P/6490P.
• 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-
mined by the BOOTSZ Fuses. Refer to the section ”Boot Loader Support – Read-While-Write
Self-Programming” on page 294 for details.
• 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 description in ”Moving Interrupts Between Application and Boot
Space” on page 59. See Code Example.
Bit 76543210
0x35 (0x55)
JTD BODS
(1)
BODSE
(1)
PUD – – IVSEL IVCE MCUCR
Read/Write R/W R R R/W R R R/W R/W
Initial Value 0 0 0 0 0 0 0 0