ATmega328 Atmel Corporation, ATmega328 Datasheet - Page 35

• Manufacturer Part Number: ATmega328
• Manufacturer: Atmel Corporation

Specifications of ATmega328

• Flash (kbytes): 32 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 20 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 23
• Ext Interrupts: 24
• Usb Speed: No
• Usb Interface: No
• Spi: 2
• Twi (i2c): 1
• Uart: 1
• 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: Yes
• Crypto Engine: No
• Sram (kbytes): 2
• Eeprom (bytes): 1024
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8 to 5.5
• Operating Voltage (vcc): 1.8 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 3
• Output Compare Channels: 6
• Input Capture Channels: 1
• Pwm Channels: 6
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

9.7
9.8
8271D–AVR–05/11
128kHz Internal Oscillator
External Clock
The 128kHz internal Oscillator is a low power Oscillator providing a clock of 128kHz. The fre-
quency is nominal at 3V and 25°C. This clock may be select as the system clock by
programming the CKSEL Fuses to “11” as shown in
Table 9-13.
Note:
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 9-14.
Note:
To drive the device from an external clock source, XTAL1 should be driven as shown in
9-4. To run the device on an external clock, the CKSEL Fuses must be programmed to “0000”
(see
Table 9-15.
Figure 9-4.
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
BOD enabled
Fast rising power
Slowly rising power
Power Conditions
Table
9-14.
9-16.
1. Note that the 128kHz oscillator is a very low power clock source, and is not designed for high
1. If the RSTDISBL fuse is programmed, this start-up time will be increased to
9-15).
accuracy.
14CK + 4.1ms to ensure programming mode can be entered.
128kHz Internal Oscillator Operating Modes
Start-up Times for the 128kHz Internal Oscillator
Crystal Oscillator Clock Frequency
External Clock Drive Configuration
Nominal Frequency
ATmega48A/PA/88A/PA/168A/PA/328/P
Frequency
0 - 20MHz
EXTERNAL
128kHz
SIGNAL
CLOCK
Start-up Time from Power-
down and Power-save
PB7
(1)
Reserved
6 CK
6 CK
6 CK
Table
XTAL2
XTAL1
GND
9-13.
Additional Delay from
14CK + 64ms
14CK + 4ms
14CK
Reset
CKSEL3...0
CKSEL3...0
(1)
0011
0000
SUT1...0
Figure
00
01
10
11
35