ATMEGA324PA-MUR Atmel, ATMEGA324PA-MUR Datasheet - Page 39

• Manufacturer Part Number: ATMEGA324PA-MUR
• Description: MCU AVR 32KB FLASH 20 MHZ 44QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA324PA-MUR

• 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: 32
• 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): 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

8.9
8.10
8.11
8152G–AVR–11/09
Timer/Counter Oscillator
Clock Output Buffer
System Clock Prescaler
Table 8-15.
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. If changes of more than 2% is
required, ensure that the MCU is kept in Reset during the changes.
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
39
ATmega164PA/324PA/644PA/1284P uses the same type of crystal oscillator for Low-frequency
Crystal Oscillator and Timer/Counter Oscillator. See
35
The device can operate its Timer/Counter2 from an external 32.768 kHz watch crystal or a exter-
nal clock source. See
Applying an external clock source to TOSC1 can be done if EXTCLK in the ASSR Register is
written to logic one. See
uously compared with the counter value (TCNT2). A match can be used to generate an Output
Compare interrupt, or to generate a waveform output on the OC2B pin.” on page 159
description on selecting external clock as input instead of a 32.768 kHz watch crystal.
The device can output the system clock on the CLKO pin. To enable the output, the CKOUT
Fuse has to be programmed. This mode is suitable when the chip clock is used to drive other cir-
cuits on the system. The clock also will be output during reset, and the normal operation of I/O
pin will be overridden when the fuse is programmed. Any clock source, including the internal RC
Oscillator, can be selected when the clock is output on CLKO. If the System Clock Prescaler is
used, it is the divided system clock that is output.
The ATmega164PA/324PA/644PA/1284P has a system clock prescaler, and the system clock
can be divided by setting the
be used to decrease the system clock frequency and the power consumption when the require-
ment 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
FLASH
When switching between prescaler settings, the System Clock Prescaler ensures that no
glitches occurs in the clock system. It also ensures that no intermediate frequency is higher than
BOD enabled
Fast rising power
Slowly rising power
for details.
for details on the oscillator and crystal requirements.
Power Conditions
are divided by a factor as shown in
Start-up Times for the External Clock Selection
”Clock Source Connections” on page 32
”The Output Compare Register B contains an 8-bit value that is contin-
ATmega164PA/324PA/644PA/1284P
Start-up Time from Power-
”CLKPR – Clock Prescale Register” on page
down and Power-save
Reserved
6 CK
6 CK
6 CK
Table 8-16 on page
”Low Frequency Crystal Oscillator” on page
Additional Delay from
”System Clock Prescaler” on page
42.
Reset (V
for details.
14CK + 4.1 ms
14CK + 65 ms
14CK
I/O
CC
, clk
= 5.0V)
ADC
41. This feature can
, clk
CPU
for further
, and clk-
SUT1..0
00
01
10
11
39