ATMEGA8HVD-4MX Atmel, ATMEGA8HVD-4MX Datasheet - Page 29

• Manufacturer Part Number: ATMEGA8HVD-4MX
• Description: MCU AVR 8K FLASH 2.1-8V 4MHZ QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA8HVD-4MX

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 4MHz
• Peripherals: POR, WDT
• Number Of I /o: 5
• Program Memory Size: 8KB (4K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 2.4 V
• Data Converters: A/D 1x10b
• Oscillator Type: Internal
• Operating Temperature: -20°C ~ 85°C
• Package / Case: 18-MLF® Exposed Pad (Staggered Leads), DFN
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32ATSTK500 - PROGRAMMER AVR STARTER KIT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Connectivity: -

8.13
8.13.1
8.13.2
8.13.3
8052B–AVR–09/08
Register Description
FOSCCAL – Fast RC Oscillator Calibration Register
MCUCR – MCU Control Register
CLKPR – Clock Prescale Register
• Bits 7:0 – FCAL7:0: Fast RC Oscillator Calibration Value
The Fast RC Oscillator Calibration Register is used to trim the Fast RC Oscillator to remove
process variations from the oscillator frequency. The factory-calibrated value is automatically
written to this register during chip reset, giving an oscillator frequency of 8.0 MHz at 85
application software can write this register to change the oscillator frequency. The oscillator
can be run-time calibrated to any frequency in the range 7.3-8.1 MHz. Calibration outside that
range is not guaranteed.
Note that this oscillator is used to time EEPROM and Flash write accesses, and these write
times will be affected accordingly. If the EEPROM or Flash are written, do not calibrate to
more than 8.1 MHz. Otherwise, the EEPROM or Flash write may fail.
The FCAL[7:5] bits determine the range of operation for the oscillator. Setting these bits to
0b000 gives the lowest frequency range, setting this bit to 0b111 gives the highest frequency
range. The frequency ranges are overlapping. A setting of for instance FOSCCAL = 0x1F
gives a higher frequency than FOSCCAL = 0x20.
The FCAL[4:0] bits are used to tune the frequency within the selected range. A setting of 0x00
gives the lowest frequency in that range, and a setting of 0x1F gives the highest frequency in
the range. Incrementing FCAL[4:0] by 1 will give a frequency increment of less than 1.5 % in
the frequency range 7.3-8.1 MHz. With an accurate time reference, an oscillator accuracy of
±1% can be achieved after calibration. The frequency will drift with temperature, so run-time
calibration will be required to maintain the accuracy. Refer to
face” on page 27
• Bit 5 – CKOE: Clock Output
When this bit is written to one, the CPU clock divided by 2 is output on the PB2 pin.
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
FCAL7
R/W
CLKPCE
7
R/W
-–
R
7
0
7
0
for details.
FCAL6
R/W
6
R
6
–
0
R
6
–
0
FCAL5
R/W
5
CKOE
R/W
R
Device Specific Calibration Value
5
–
0
5
0
FCAL4
R/W
4
R
4
–
0
PUD
R/W
4
0
FCAL3
R/W
3
R
3
–
0
R
3
–
0
ATmega4HVD/8HVD
FCAL2
R/W
2
R
2
–
0
”OSI – Oscillator Sampling Inter-
R
2
–
0
FCAL1
CLKPS1
R/W
R/W
1
1
1
R
1
–
0
FCAL0
CLKPS0
R/W
0
R/W
0
1
R
0
–
0
FOSCCAL
°
MCUCR
CLKPR
C. The
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