ATMEGA8A-AUR Atmel, ATMEGA8A-AUR Datasheet - Page 31

• Manufacturer Part Number: ATMEGA8A-AUR
• Description: MCU AVR 8KB FLASH 16MHZ 32TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA8A-AUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 23
• Program Memory Size: 8KB (4K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 1K 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: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8.9
8.9.1
8159D–AVR–02/11
Register Description
OSCCAL – Oscillator Calibration Register
• Bits 7:0 – CAL7:0: Oscillator Calibration Value
Writing the calibration byte to this address will trim the Internal Oscillator to remove process vari-
ations from the Oscillator frequency. During Reset, the 1MHz calibration value which is located
in the signature row High byte (address 0x00) is automatically loaded into the OSCCAL Regis-
ter. If the internal RC is used at other frequencies, the calibration values must be loaded
manually. This can be done by first reading the signature row by a programmer, and then store
the calibration values in the Flash or EEPROM. Then the value can be read by software and
loaded into the OSCCAL Register. When OSCCAL is zero, the lowest available frequency is
chosen. Writing non-zero values to this register will increase the frequency of the Internal Oscil-
lator. Writing 0xFF to the register gives the highest available frequency. The calibrated Oscillator
is used to time EEPROM and Flash access. If EEPROM or Flash is written, do not calibrate to
more than 10% above the nominal frequency. Otherwise, the EEPROM or Flash write may fail.
Note that the Oscillator is intended for calibration to 1.0, 2.0, 4.0, or 8.0 MHz. Tuning to other
values is not guaranteed, as indicated in
Table 8-11.
Bit
Read/Write
Initial Value
OSCCAL Value
0x7F
0xFF
0x00
Internal RC Oscillator Frequency Range
CAL7
R/W
7
Min Frequency in Percentage of
CAL6
R/W
6
Nominal Frequency (%)
CAL5
R/W
5
Device Specific Calibration Value
100
50
75
Table
CAL4
R/W
4
8-11.
CAL3
R/W
3
CAL2
R/W
Max Frequency in Percentage of
2
Nominal Frequency (%)
CAL1
R/W
1
ATmega8A
100
150
200
CAL0
R/W
0
OSCCAL
31