ATMEGA644A-AU Atmel, ATMEGA644A-AU Datasheet - Page 153
![IC MCU AVR 64K FLASH 44TQFP](/photos/6/70/67042/313-44-tqfp_sml.jpg)
ATMEGA644A-AU
Manufacturer Part Number
ATMEGA644A-AU
Description
IC MCU AVR 64K FLASH 44TQFP
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA644A-AU
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
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
44-TQFP, 44-VQFP
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
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Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
ATMEGA644A-AU
Manufacturer:
Atmel
Quantity:
135
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16.10 Timer/Counter Prescaler
8272A–AVR–01/10
Figure 16-12. Prescaler for Timer/Counter2
The clock source for Timer/Counter2 is named clk
system I/O clock clk
clocked from the TOSC1 pin. This enables use of Timer/Counter2 as a Real Time Counter
(RTC). When AS2 is set, pins TOSC1 and TOSC2 are disconnected from Port C. A crystal can
then be connected between the TOSC1 and TOSC2 pins to serve as an independent clock
source for Timer/Counter2. The Oscillator is optimized for use with a 32.768 kHz crystal. By set-
ting the EXCLK bit in the ASSR a 32 kHz external clock can be applied. See
Asynchronous Status Register” on page 158
For Timer/Counter2, the possible prescaled selections are: clk
clk
Setting the PSRASY bit in GTCCR resets the prescaler. This allows the user to operate with a
predictable prescaler.
164A/164PA/324A/324PA/644A/644PA/1284/1284P
T2S
/128, clk
PSRASY
TOSC1
clk
CS20
CS21
CS22
AS2
I/O
T2S
/256, and clk
IO
. By setting the AS2 bit in ASSR, Timer/Counter2 is asynchronously
clk
T2S
T2S
/1024. Additionally, clk
Clear
for details.
TIMER/COUNTER2 CLOCK SOURCE
T2S
0
. clk
10-BIT T/C PRESCALER
T2S
T2S
clk
as well as 0 (stop) may be selected.
T2
is by default connected to the main
T2S
/8, clk
T2S
/32, clk
”ASSR –
T2S
/64,
153
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