ATMEGA329P-20MN Atmel, ATMEGA329P-20MN Datasheet - Page 33

• Manufacturer Part Number: ATMEGA329P-20MN
• Description: IC MCU AVR 32K 20MHZ 64QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA329P-20MN

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, LCD, POR, PWM, WDT
• Number Of I /o: 54
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 1K x 8
• Ram Size: 2K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-MLF®, 64-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8.8
8.9
8.10
8021G–AVR–03/11
Clock Output Buffer
Timer/Counter Oscillator
System Clock Prescaler
Table 8-12.
When applying an external clock, it is required to avoid sudden changes in the applied clock fre-
quency to ensure stable operation of the MCU. A variation in frequency of more than 2% from
one clock cycle to the next can lead to unpredictable behavior. It is required to ensure that the
MCU is kept in Reset during such changes in the clock frequency.
Note that the System Clock Prescaler can be used to implement run-time changes of the internal
clock frequency while still ensuring stable operation. Refer to
33
When the CKOUT Fuse is programmed, the system Clock will be output on CLKO. This mode is
suitable when the chip clock is used to drive other circuits on the system. The clock will be out-
put also during reset and the normal operation of I/O pin will be overridden when the fuse is
programmed. Any clock source, including internal RC Oscillator, can be selected when CLKO
serves as clock output. If the System Clock Prescaler is used, it is the divided system clock that
is output when the CKOUT Fuse is programmed.
ATmega329P/3290P uses the same crystal oscillator for Low-frequency Oscillator and
Timer/Counter Oscillator. See
oscillator and crystal requirements.
ATmega329P/3290P share the Timer/Counter Oscillator Pins (TOSC1 and TOSC2) with XTAL1
and XTAL2. When using the Timer/Counter Oscillator, the system clock needs to be four times
the oscillator frequency. Due to this and the pin sharing, the Timer/Counter Oscillator can only
be used when the Calibrated Internal RC Oscillator is selected as system clock source.
Applying an external clock source to TOSC1 can be done if EXTCLK in the ASSR Register is
written to logic one. See
description on selecting external clock as input instead of a 32.768kHz watch crystal.
The ATmega329P/3290P system clock can be divided by setting the Clock Prescale Register –
CLKPR. This feature can be used to decrease power consumption when the requirement for
processing power is low. This can be used with all clock source options, and it will affect the
clock frequency of the CPU and all synchronous peripherals. clk
are divided by a factor as shown in
SUT1..0
for details.
00
01
10
11
Start-up Time from Power-
Start-up Times for the External Clock Selection
down and Power-save
6 CK
6 CK
6 CK
”Asynchronous Operation of Timer/Counter2” on page 152
”Low-frequency Crystal Oscillator” on page 30
Table 8-13 on page
Additional Delay from
Reset (V
Reserved
14CK + 4.1ms
14CK + 65ms
14CK
36.
CC
ATmega329P/3290P
= 5.0V)
”System Clock Prescaler” on page
I/O
, clk
BOD enabled
Fast rising power
Slowly rising power
ADC
Recommended Usage
, clk
for details on the
CPU
, and clk
for further
FLASH
33