ATMEGA328P-20PU Atmel, ATMEGA328P-20PU Datasheet - Page 33

• Manufacturer Part Number: ATMEGA328P-20PU
• Manufacturer: Atmel

Specifications of ATMEGA328P-20PU

• Cpu Family: ATmega
• Device Core: AVR
• Device Core Size: 8b
• Frequency (max): 20MHz
• Interface Type: SPI/TWI/USART
• Program Memory Type: Flash
• Program Memory Size: 32KB
• Total Internal Ram Size: 2KB
• # I/os (max): 23
• Number Of Timers - General Purpose: 3
• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 2.7V
• On-chip Adc: 6-chx10-bit
• Instruction Set Architecture: RISC
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Through Hole
• Pin Count: 28
• Package Type: PDIP
• Lead Free Status / Rohs Status: Compliant

8.6
8025K–AVR–10/09
Calibrated Internal RC Oscillator
Table 8-10.
Note:
By default, the Internal RC Oscillator provides an approximate 8.0 MHz clock. Though voltage
and temperature dependent, this clock can be very accurately calibrated by the user. See
28-1 on page 312
See
This clock may be selected as the system clock by programming the CKSEL Fuses as shown in
Table
the pre-programmed calibration value into the OSCCAL Register and thereby automatically cal-
ibrates the RC Oscillator. The accuracy of this calibration is shown as Factory calibration in
Table 28-1 on page
By changing the OSCCAL register from SW, see
page
The accuracy of this calibration is shown as User calibration in
When this Oscillator is used as the chip clock, the Watchdog Oscillator will still be used for the
Watchdog Timer and for the Reset Time-out. For more information on the pre-programmed cali-
bration value, see the section
Table 8-11.
Notes:
When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in
Table 8-12 on page
Table 8-12.
Note:
CKSEL3..0
Power Conditions
BOD enabled
Fast rising power
Slowly rising power
0100
0101
”System Clock Prescaler” on page 35
37, it is possible to get a higher calibration accuracy than by using the factory calibration.
8-11. If selected, it will operate with no external components. During reset, hardware loads
(1)
1. This option should only be used if frequency stability at start-up is not important for the
1. This is the recommended CKSEL settings for the different frequency ranges.
2. If 8 MHz frequency exceeds the specification of the device (depends on V
1. If the RSTDISBL fuse is programmed, this start-up time will be increased to
2.
The device is shipped with this option selected.
application
Frequency Range
Fuse can be programmed in order to divide the internal frequency by 8.
14CK + 4.1 ms to ensure programming mode can be entered.
Start-up Times for the Low-frequency Crystal Oscillator Clock Selection
Internal Calibrated RC Oscillator Operating Modes
Start-up times for the internal calibrated RC Oscillator clock selection
for more details. The device is shipped with the CKDIV8 Fuse programmed.
7.3 - 8.1
312.
33.
Power-down and Power-save
Start-up Time from
(1)
Start-up Time from Power-
”Calibration Byte” on page
32K CK
(MHz)
1K CK
down and Power-save
Reserved
6 CK
6 CK
6 CK
for more details.
”OSCCAL – Oscillator Calibration Register” on
ATmega48P/88P/168P
Recommended Usage
Stable frequency at start-up
293.
Additional Delay from
Reset (V
Table 28-1 on page
14CK + 65 ms
14CK + 4.1 ms
(2)
CKSEL3..0
14CK
0010
CC
(1)
= 5.0V)
(2)
CC
), the CKDIV8
312.
SUT1..0
00
01
10
11
Table
33