61
2513L–AVR–03/2013
ATmega162/V
When the BOOTRST Fuse is programmed, the boot section size set to 2K bytes and the IVSEL
bit in the GICR Register is set before any interrupts are enabled, the most typical and general
program setup for the Reset and Interrupt Vector Addresses is:
Address
Labels
Code
Comments
.org 0x1C00
0x1C00
jmp
RESET
; Reset handler
0x1C02
jmp
EXT_INT0
; IRQ0 Handler
0x1C04
jmp
EXT_INT1
; IRQ1 Handler
...
....
..
;
0x1C36
jmp
SPM_RDY
; Store Program Memory Ready Handler
;
0x1C38
RESET:
ldi
r16,high(RAMEND) ; Main program start
0x1C39
out
SPH,r16
; Set Stack Pointer to top of RAM
0x1C3A
ldi
r16,low(RAMEND)
0x1C3B
out
SPL,r16
0x1C3C
sei
; Enable interrupts
0x1C3D
<instr>
xxx
Moving Interrupts
Between Application
and Boot Space
The General Interrupt Control Register controls the placement of the Interrupt Vector table.
General Interrupt
Control Register –
GICR
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-
tables, a special write procedure must be followed to change the IVSEL bit:
1.
Write the Interrupt Vector Change Enable (IVCE) bit to one.
2.
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, 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 pro-
grammed, 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 dis-
Bit
7
654
32
10
INT1
INT0
INT2
PCIE1
PCIE0
–
IVSEL
IVCE
GICR
Read/Write
R/W
R
R/W
Initial Value
0