ATMEGA645V-8MI Atmel, ATMEGA645V-8MI Datasheet - Page 27

• Manufacturer Part Number: ATMEGA645V-8MI
• Description: IC AVR MCU FLASH 64K 1.8V 64QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA645V-8MI

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 8MHz
• Connectivity: SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, 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): 1.8 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: Contains lead / RoHS non-compliant

8.1.4
8.1.5
8.2
8.2.1
2570M–AVR–04/11
Clock Sources
Asynchronous Timer Clock – clk
ADC Clock – clk
Default Clock Source
The Asynchronous Timer clock allows the Asynchronous Timer/Counter to be clocked directly
from an external clock or an external 32kHz clock crystal. The dedicated clock domain allows
using this Timer/Counter as a real-time counter even when the device is in sleep mode.
The ADC is provided with a dedicated clock domain. This allows halting the CPU and I/O clocks
in order to reduce noise generated by digital circuitry. This gives more accurate ADC conversion
results.
The device has the following clock source options, selectable by Flash Fuse bits as shown
below. The clock from the selected source is input to the AVR clock generator, and routed to the
appropriate modules.
Table 8-1.
Note:
The various choices for each clocking option is given in the following sections. When the CPU
wakes up from Power-down or Power-save, the selected clock source is used to time the start-
up, ensuring stable Oscillator operation before instruction execution starts. When the CPU starts
from reset, there is an additional delay allowing the power to reach a stable level before com-
mencing normal operation. The Watchdog Oscillator is used for timing this real-time part of the
start-up time. The number of WDT Oscillator cycles used for each time-out is shown in
on page
cal Characteristics” on page
Table 8-2.
The device is shipped with CKSEL = “0010”, SUT = “10”, and CKDIV8 programmed. The default
clock source setting is the Internal RC Oscillator with longest start-up time and an initial system
clock prescaling of 8. This default setting ensures that all users can make their desired clock
source setting using an In-System or Parallel programmer.
ADC
Device Clocking Option
External Crystal/Ceramic Resonator
External Low-frequency Crystal
Calibrated Internal RC Oscillator
External Clock
Reserved
Typ Time-out (V
For all fuses “1” means unprogrammed while “0” means programmed.
27. The frequency of the Watchdog Oscillator is voltage dependent as shown in
4.1ms
65ms
Device Clocking Options Select
Number of Watchdog Oscillator Cycles
CC
ASY
= 5.0V)
306.
Typ Time-out (V
4.3ms
69ms
ATmega325/3250/645/6450
(Note:)
CC
= 3.0V)
0011, 0001, 0101, 0100
Number of Cycles
64K (65,536)
4K (4,096)
1111 - 1000
0111 - 0110
CKSEL3..0
0010
0000
Table 8-2
“Typi-
27