ATMEGA644PA-MUR Atmel, ATMEGA644PA-MUR Datasheet - Page 142
![IC MCU AVR 64K FLASH 44VQFN](/photos/12/13/121316/313-44-qfn_sml.jpg)
ATMEGA644PA-MUR
Manufacturer Part Number
ATMEGA644PA-MUR
Description
IC MCU AVR 64K FLASH 44VQFN
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA644PA-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
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-VQFN Exposed Pad
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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16.4
16.5
8272A–AVR–01/10
Counter Unit
Output Compare Unit
The main part of the 8-bit Timer/Counter is the programmable bi-directional counter unit.
16-2
Figure 16-2. Counter Unit Block Diagram
Signal description (internal signals):
Depending on the mode of operation used, the counter is cleared, incremented, or decremented
at each timer clock (clk
selected by the Clock Select bits (CS22:0). When no clock source is selected (CS22:0 = 0) the
timer is stopped. However, the TCNT2 value can be accessed by the CPU, regardless of
whether clk
count operations.
The counting sequence is determined by the setting of the WGM21 and WGM20 bits located in
the Timer/Counter Control Register (TCCR2A) and the WGM22 located in the Timer/Counter
Control Register B (TCCR2B). There are close connections between how the counter behaves
(counts) and how waveforms are generated on the Output Compare outputs OC2A and OC2B.
For more details about advanced counting sequences and waveform generation, see
Operation” on page
The Timer/Counter Overflow Flag (TOV2) is set according to the mode of operation selected by
the WGM22:0 bits. TOV2 can be used for generating a CPU interrupt.
The 8-bit comparator continuously compares TCNT2 with the Output Compare Register
(OCR2A and OCR2B). Whenever TCNT2 equals OCR2A or OCR2B, the comparator signals a
match. A match will set the Output Compare Flag (OCF2A or OCF2B) at the next timer clock
cycle. If the corresponding interrupt is enabled, the Output Compare Flag generates an Output
Compare interrupt. The Output Compare Flag is automatically cleared when the interrupt is exe-
cuted. Alternatively, the Output Compare Flag can be cleared by software by writing a logical
one to its I/O bit location. The Waveform Generator uses the match signal to generate an output
164A/164PA/324A/324PA/644A/644PA/1284/1284P
shows a block diagram of the counter and its surrounding environment.
count
direction
clear
clk
top
bottom
Tn
T2
DATA BUS
is present or not. A CPU write overrides (has priority over) all counter clear or
TCNTn
145.
T2
). clk
Increment or decrement TCNT2 by 1.
Selects between increment and decrement.
Clear TCNT2 (set all bits to zero).
Timer/Counter clock, referred to as clk
Signalizes that TCNT2 has reached maximum value.
Signalizes that TCNT2 has reached minimum value (zero).
T2
direction
can be generated from an external or internal clock source,
count
clear
bottom
Control Logic
top
TOVn
(Int.Req.)
clk
Tn
Prescaler
T2
in the following.
Oscillator
T/C
clk
I/O
TOSC2
TOSC1
”Modes of
Figure
142
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