ATMEGA645A-AU Atmel, ATMEGA645A-AU Datasheet - Page 107

• Manufacturer Part Number: ATMEGA645A-AU
• Description: IC MCU AVR 64K FLASH 64TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA645A-AU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 54
• 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-TQFP
• Processor Series: ATmega
• Core: AVR
• Data Bus Width: 8 bit
• Data Ram Size: 4 KB
• Interface Type: SPI, USART
• Maximum Clock Frequency: 16 MHz
• Number Of Programmable I/os: 54
• Number Of Timers: 3
• Operating Supply Voltage: 3.3 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Operating Temperature Range: - 40 C to + 85 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

14.9.2
14.9.3
14.9.4
8285B–AVR–03/11
TCNT0 – Timer/Counter Register
OCR0A – Output Compare Register A
TIMSK0 – Timer/Counter 0 Interrupt Mask Register
ATmega165A/165PA/325A/325PA/3250A/3250PA/6
Table 14-6.
If external pin modes are used for the Timer/Counter0, transitions on the T0 pin will clock the
counter even if the pin is configured as an output. This feature allows software control of the
counting.
The Timer/Counter Register gives direct access, both for read and write operations, to the
Timer/Counter unit 8-bit counter. Writing to the TCNT0 Register blocks (removes) the compare
match on the following timer clock. Modifying the counter (TCNT0) while the counter is running,
introduces a risk of missing a compare match between TCNT0 and the OCR0A Register.
The Output Compare Register A contains an 8-bit value that is continuously compared with the
counter value (TCNT0). A match can be used to generate an Output Compare interrupt, or to
generate a waveform output on the OC0A pin.
• Bit 1 – OCIE0A: Timer/Counter0 Output Compare Match A Interrupt Enable
When the OCIE0A bit is written to one, and the I-bit in the Status Register is set (one), the
Timer/Counter0 Compare Match A interrupt is enabled. The corresponding interrupt is executed
Bit
0x26 (0x46)
Read/Write
Initial Value
Bit
0x27 (0x47)
Read/Write
Initial Value
Bit
(0x6E)
Read/Write
Initial Value
CS02
0
0
0
0
1
1
1
1
CS01
0
0
1
1
0
0
1
1
Clock Select Bit Description
R/W
R/W
R
7
0
7
0
7
–
0
CS00
0
1
0
1
0
1
0
1
R/W
R/W
R
6
0
6
0
6
–
0
Description
No clock source (Timer/Counter stopped)
clk
clk
clk
clk
clk
External clock source on T0 pin. Clock on falling edge.
External clock source on T0 pin. Clock on rising edge.
I/O
I/O
I/O
I/O
I/O
/(No prescaling)
/8 (From prescaler)
/64 (From prescaler)
/256 (From prescaler)
/1024 (From prescaler)
R/W
R/W
R
5
0
5
0
5
–
0
R/W
R/W
R
4
0
4
0
4
–
0
OCR0A[7:0]
TCNT0[7:0]
R/W
R/W
R
3
0
3
0
3
–
0
R/W
R/W
R
2
0
2
0
2
–
0
OCIE0A
R/W
R/W
R/W
1
0
1
0
1
0
TOIE0
R/W
R/W
R/W
0
0
0
0
0
0
OCR0A
TIMSK0
TCNT0
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