参数资料
型号: IV80C31-25R
厂商: ATMEL CORP
元件分类: 微控制器/微处理器
英文描述: 8-BIT, 25 MHz, MICROCONTROLLER, PQFP44
封装: 1.40 MM HEIGHT, QFP-44
文件页数: 22/91页
文件大小: 19688K
代理商: IV80C31-25R
33
7707F–AVR–11/10
AT90USB82/162
3. If 8 MHz frequency exceeds the specification of the device (depends on VCC), the CKDIV8
Fuse can be programmed in order to divide the internal frequency by 8.
When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in
Note:
1. The device is shipped with this option selected.
6.5.1
Oscillator Calibration Register – OSCCAL
Bits 7..0 – CAL7..0: Oscillator Calibration Value
The Oscillator Calibration Register is used to trim the Calibrated Internal RC Oscillator to
remove process variations from the oscillator frequency. The factory-calibrated value is automat-
ically written to this register during chip reset, giving an oscillator frequency of 8.0 MHz at 25°C.
The application software can write this register to change the oscillator frequency. The oscillator
can be calibrated to any frequency in the range 7.3 - 8.1 MHz within ±1% accuracy. 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 8.8 MHz. Otherwise, the EEPROM or Flash write may fail.
The CAL7 bit determines the range of operation for the oscillator. Setting this bit to 0 gives the
lowest frequency range, setting this bit to 1 gives the highest frequency range. The two fre-
quency ranges are overlapping, in other words a setting of OSCCAL = 0x7F gives a higher
frequency than OSCCAL = 0x80.
The CAL6..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 0x7F gives the highest frequency in the
range. Incrementing CAL6..0 by 1 will give a frequency increment of less than 2% in the fre-
quency range 7.3 - 8.1 MHz.
Table 6-7.
Start-up times for the internal calibrated RC Oscillator clock selection
Power Conditions
Start-up Time from Power-
down and Power-save
Additional Delay from
Reset (V
CC = 5.0V)
SUT1..0
BOD enabled
6 CK
14 CK
00
Fast rising power
6 CK
14 CK + 4.1 ms
01
Slowly rising power
6 CK
14 CK + 65 ms(1)
10
Reserved
11
Bit
7654
3
2
1
0
CAL7
CAL6
CAL5
CAL4
CAL3
CAL2
CAL1
CAL0
OSCCAL
Read/Write
R/WR/W
Initial Value
Device Specific Calibration Value
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