ATMEGA48PA-AN Atmel, ATMEGA48PA-AN Datasheet - Page 68

• Manufacturer Part Number: ATMEGA48PA-AN
• Description: MCU AVR 4KB FLASH 20MHZ 32TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA48PA-AN

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 23
• Program Memory Size: 4KB (2K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

11.5
11.5.1
11.5.2
8161D–AVR–10/09
Register Description
Moving Interrupts Between Application and Boot Space, ATmega88PA, ATmega168PA and ATmega328P
MCUCR – MCU Control Register
When the BOOTRST Fuse is programmed, the Boot section size set to 2K bytes and the IVSEL
bit in the MCUCR Register is set before any interrupts are enabled, the most typical and general
program setup for the Reset and Interrupt Vector Addresses in ATmega328P is:
The MCU Control Register controls the placement of the Interrupt Vector table.
• 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
Self-Programming, ATmega88PA, ATmega168PA and ATmega328P” on page 277
To avoid unintentional changes of Interrupt Vector tables, a special write procedure must be fol-
lowed to change the IVSEL bit:
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
Bit
0x35 (0x55)
Read/Write
Initial Value
0x3C01
0x3C02
0x3C03
0x3C04
0x3C05
Address Labels Code
;
.org 0x3C00
0x3C00
0x3C02
0x3C04
...
0x3C32
;
0x3C33
0x3C34
0x3C35
0x3C36
0x3C37
0x3C38
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.
RESET: ldi
R
7
–
0
out
ldi
out
sei
<instr>
jmp
jmp
jmp
...
jmp
out
ldi
out
sei
<instr>
BODS
R
6
0
SPH,r16
r16,low(RAMEND)
SPL,r16
RESET
EXT_INT0
EXT_INT1
...
SPM_RDY
r16,high(RAMEND); Main program start
SPH,r16
r16,low(RAMEND)
SPL,r16
xxx
xxx
BODSE
ATmega48PA/88PA/168PA/328P
R
5
0
PUD
R/W
4
0
; Set Stack Pointer to top of RAM
; Enable interrupts
Comments
; Reset handler
; IRQ0 Handler
; IRQ1 Handler
;
; Store Program Memory Ready Handler
; Set Stack Pointer to top of RAM
; Enable interrupts
”Boot Loader Support – Read-While-Write
R
3
–
0
R
2
–
0
IVSEL
R/W
1
0
IVCE
R/W
0
0
for details.
MCUCR
68