ATMEGA325_14 Datasheet, PDF (6/362 Pages) ATMEL Corporation – High Endurance Non-volatile Memory Segments

ATmega325/3250/645/6450
2.2 Comparison between ATmega325, ATmega3250, ATmega645 and ATmega6450
The ATmega325, ATmega3250, ATmega645, and ATmega6450 differ only in memory sizes, pin
count and pinout. Table 2-1 on page 6 summarizes the different configurations for the four
devices.
Table 2-1. Configuration Summary
Device
ATmega325
ATmega3250
ATmega645
ATmega6450
Flash
32Kbytes
32Kbytes
64Kbytes
64Kbytes
EEPROM
1Kbytes
1Kbytes
2Kbytes
2Kbytes
RAM
2Kbytes
2Kbytes
4Kbytes
4Kbytes
General Purpose
I/O Pins
54
69
54
69
2.3 Pin Descriptions
The following section describes the I/O-pin special functions.
2.3.1
V_CC
Digital supply voltage.
2.3.2 GND
Ground.
2.3.3
Port A (PA7..PA0)
Port A is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The
Port A output buffers have symmetrical drive characteristics with both high sink and source
capability. As inputs, Port A pins that are externally pulled low will source current if the pull-up
resistors are activated. The Port A pins are tri-stated when a reset condition becomes active,
even if the clock is not running.
2.3.4
Port B (PB7..PB0)
Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The
Port B output buffers have symmetrical drive characteristics with both high sink and source
capability. As inputs, Port B pins that are externally pulled low will source current if the pull-up
resistors are activated. The Port B pins are tri-stated when a reset condition becomes active,
even if the clock is not running.
Port B has better driving capabilities than the other ports.
Port B also serves the functions of various special features of the Atmel
ATmega325/3250/645/6450 as listed on page 68.
2.3.5
Port C (PC7..PC0)
Port C is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The
Port C output buffers have symmetrical drive characteristics with both high sink and source
capability. As inputs, Port C pins that are externally pulled low will source current if the pull-up
resistors are activated. The Port C pins are tri-stated when a reset condition becomes active,
even if the clock is not running.
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2570N–AVR–05/11