ATmega128A Atmel Corporation, ATmega128A Datasheet - Page 109

• Manufacturer Part Number: ATmega128A
• Manufacturer: Atmel Corporation

Specifications of ATmega128A

• Flash (kbytes): 128 Kbytes
• Pin Count: 64
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 53
• Ext Interrupts: 8
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Uart: 2
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 4
• Eeprom (bytes): 4096
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 4
• Output Compare Channels: 8
• Input Capture Channels: 2
• Pwm Channels: 7
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

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
109