ATMEGA128A-ANR Atmel, ATMEGA128A-ANR Datasheet - Page 109

• Manufacturer Part Number: ATMEGA128A-ANR
• Description: IC MCU AVR 128K FLASH 64TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA128A-ANR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: EBI/EMI, I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 128KB (64K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 4K 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: 64-TQFP
• Core: AVR8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

14.11.2
14.11.3
14.11.4
8151H–AVR–02/11
TCNT0 - Timer/Counter Register
OCR0 - Output Compare Register
ASSR - Asynchronous Status Register
Table 14-6.
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 OCR0 Register.
The Output Compare Register 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 OC0 pin.
• Bit 3 – AS0: Asynchronous Timer/Counter0
When AS0 is written to zero, Timer/Counter0 is clocked from the I/O clock, clk
written to one, Timer/Counter is clocked from a crystal Oscillator connected to the Timer Oscilla-
tor 1 (TOSC1) pin. When the value of AS0 is changed, the contents of TCNT0, OCR0, and
TCCR0 might be corrupted.
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
CS02
0
0
0
0
1
1
1
1
Clock Select Bit Description
R
R/W
R/W
7
–
0
CS01
7
0
7
0
0
0
1
1
0
0
1
1
R
6
–
0
R/W
R/W
6
0
6
0
CS00
0
1
0
1
0
1
0
1
R
5
–
0
R/W
R/W
5
0
5
0
Description
No clock source (Timer/Counter stopped)
clk
clk
clk
clk
clk
clk
clk
R
4
–
0
T
T
T0S
T0S
T0S
T0S
T0S
R/W
R/W
0
0
S
S
4
0
4
0
/256 (From prescaler)
/1024 (From prescaler)
TCNT0[7:0]
OCR0[7:0]
/(No prescaling)
/8 (From prescaler)
/32 (From prescaler)
/64 (From prescaler)
/128 (From prescaler)
AS0
R/W
3
0
R/W
R/W
3
0
3
0
TCN0UB
R
2
0
R/W
R/W
2
0
2
0
OCR0UB
R
1
0
ATmega128A
R/W
R/W
1
0
1
0
TCR0UB
I/O
R
R/W
R/W
0
0
0
0
0
0
. When AS0 is
TCNT0
ASSR
OCR0
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