ATmega128A Atmel Corporation, ATmega128A Datasheet - Page 39

• 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

8.2
8.3
8.4
8151H–AVR–02/11
Clock Sources
Default Clock Source
Crystal Oscillator
The device has the following clock source options, selectable by Flash fuse bits as shown
below. The clock from the selected source is input to the Atmel
routed to the appropriate modules.
Table 8-1.
Note:
The various choices for each clocking option is given in the following sections. When the CPU
wakes up from Power-down or Power-save, the selected clock source is used to time the start-
up, ensuring stable Oscillator operation before instruction execution starts. When the CPU starts
from reset, there is as an additional delay allowing the power to reach a stable level before com-
mencing normal operation. The Watchdog Oscillator is used for timing this real-time part of the
start-up time. The number of WDT Oscillator cycles used for each time-out is shown in
2. The frequency of the Watchdog Oscillator is voltage dependent as shown in the
Characteristics” on page
Table 8-2.
The device is shipped with CKSEL = “0001” and SUT = “10”. The default clock source setting is
therefore the Internal RC Oscillator with longest startup time. This default setting ensures that all
users can make their desired clock source setting using an In-System or Parallel Programmer.
XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier which can be con-
figured for use as an On-chip Oscillator, as shown in
ceramic resonator may be used. The CKOPT fuse selects between two different Oscillator
Amplifier modes. When CKOPT is programmed, the Oscillator output will oscillate will a full rail-
to-rail swing on the output. This mode is suitable when operating in a very noisy environment or
when the output from XTAL2 drives a second clock buffer. This mode has a wide frequency
range. When CKOPT is unprogrammed, the Oscillator has a smaller output swing. This reduces
power consumption considerably. This mode has a limited frequency range and it can not be
used to drive other clock buffers.
For resonators, the maximum frequency is 8MHz with CKOPT unprogrammed and 16MHz with
CKOPT programmed. C1 and C2 should always be equal for both crystals and resonators. The
optimal value of the capacitors depends on the crystal or resonator in use, the amount of stray
Device Clocking Option
External Crystal/Ceramic Resonator
External Low-frequency Crystal
External RC Oscillator
Calibrated Internal RC Oscillator
External Clock
Typical Time-out (V
1. For all fuses “1” means unprogrammed while “0” means programmed.
Device Clocking Options Select
Number of Watchdog Oscillator Cycles
4.1ms
65ms
CC
338.
= 5.0V)
Typical Time-Out (V
4.3ms
69ms
Figure
CC
= 3.0V)
8-2. Either a quartz crystal or a
®
AVR
ATmega128A
®
clock generator, and
Number of Cycles
CKSEL3:0
1111 - 1010
1000 - 0101
0100 - 0001
64K (65,536)
4K (4,096)
1001
0000
(1)
Table 8-
“Typical
39