ATMEGA649-16MUR Atmel, ATMEGA649-16MUR Datasheet - Page 31

• Manufacturer Part Number: ATMEGA649-16MUR
• Description: MCU AVR 64KB FLASH 16MHZ 64QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA649-16MUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, LCD, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 64KB (32K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 2K x 8
• Ram Size: 4K 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: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8.6
8.7
2552K–AVR–04/11
External Clock
Clock Output Buffer
To drive the device from an external clock source, XTAL1 should be driven as shown in
8-3. To run the device on an external clock, the CKSEL Fuses must be programmed to “0000”.
Figure 8-3.
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 8-9.
Table 8-10.
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
32
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
SUT1..0
for details.
00
01
10
11
8-10.
Start-up Time from Power-
CKSEL3..0
down and Power-save
External Clock Drive Configuration
Crystal Oscillator Clock Frequency
Start-up Times for the External Clock Selection
0000
6 CK
6 CK
6 CK
EXTERNAL
SIGNAL
CLOCK
NC
Additional Delay from
Reset (V
Reserved
ATmega329/3290/649/6490
14CK + 4.1ms
14CK + 65ms
14CK
CC
Frequency Range
= 5.0V)
XTAL2
XTAL1
GND
0 - 16MHz
“System Clock Prescaler” on page
BOD enabled
Fast rising power
Recommended Usage
Slowly rising power
Figure
31