4
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P [DATASHEET]
8285E–AVR–02/2013
2.
Overview
The Atmel ATmega165A/165PA/325A/325PA/3250A/3250PA/645A/645P/6450A/6450P is a low-power CMOS 8-bit micro-
controller based on the AVR enhanced RISC architecture. By executing powerful instructions in a single clock cycle, this
microcontroller achieves throughputs approaching 1 MIPS per MHz allowing the system designer to optimize power con-
sumption versus processing speed.
2.1
Block diagram
Figure 2-1.
Block diagram.
The AVR core combines a rich instruction set with 32 general purpose working registers. All the 32 registers are
directly connected to the Arithmetic Logic Unit (ALU), allowing two independent registers to be accessed in one
single instruction executed in one clock cycle. The resulting architecture is more code efficient while achieving
throughputs up to ten times faster than conventional CISC microcontrollers.
PROGRAM
COUNTER
INTERNAL
OSCILLATOR
WATCHDOG
TIMER
STACK
POINTER
PROGRAM
FLASH
MCU CONTROL
REGISTER
SRAM
GENERAL
PURPOSE
REGISTERS
INSTRUCTION
REGISTER
TIMER/
COUNTERS
INSTRUCTION
DECODER
DATA DIR.
REG. PORTB
DATA DIR.
REG. PORTE
DATA DIR.
REG. PORTA
DATA DIR.
REG. PORTD
DATA REGISTER
PORTB
DATA REGISTER
PORTE
DATA REGISTER
PORTA
DATA REGISTER
PORTD
TIMING AND
CONTROL
OSCILLATOR
INTERRUPT
UNIT
EEPROM
SPI
USART
STATUS
REGISTER
Z
Y
X
ALU
PORTB DRIVERS
PORTE DRIVERS
PORTA DRIVERS
PORTF DRIVERS
PORTD DRIVERS
PORTC DRIVERS
PB0 - PB7
PE0 - PE7
PA0 - PA7
PF0 - PF7
VCC
GND
XT
AL1
XT
AL2
CONTROL
LINES
+
-
A
N
ALOG
COMP
ARA
T
O
R
PC0 - PC7
8-BIT DATA BUS
RESET
CALIB. OSC
DATA DIR.
REG. PORTC
DATA REGISTER
PORTC
ON-CHIP DEBUG
JTAG TAP
PROGRAMMING
LOGIC
BOUNDARY-
SCAN
DATA DIR.
REG. PORTF
DATA REGISTER
PORTF
ADC
PD0 - PD7
DATA DIR.
REG. PORTG
DATA REG.
PORTG
PORTG DRIVERS
PG0 - PG4
AGND
AREF
AVCC
UNIVERSAL
SERIAL INTERFACE
AVR CPU
POR
TH
DRI
V
ERS
PH0
-
PH7
D
A
T
A
DIR.
REG.
POR
T
H
D
A
T
A
REGISTER
POR
T
H
POR
TJ
DRI
V
ERS
PJ0
-
PJ6
D
A
T
A
DIR.
REG.
POR
T
J
D
A
T
A
REGISTER
POR
T
J