AT90USB647-MU Atmel, AT90USB647-MU Datasheet - Page 45

• Manufacturer Part Number: AT90USB647-MU
• Description: MCU, 8BIT, 64K FLASH, USB, 64QFN
• Manufacturer: Atmel

Specifications of AT90USB647-MU

• Controller Family/series: AT90
• No. Of I/o's: 48
• Eeprom Memory Size: 2KB
• Ram Memory Size: 4KB
• Cpu Speed: 16MHz
• No. Of: RoHS Compliant
• Core Size: 8bit
• Program Memory Size: 64KB
• Oscillator Type: External, Internal
• Package: 64QFN EP
• Device Core: AVR
• Family Name: AT90
• Maximum Speed: 20 MHz
• Ram Size: 4 KB
• Operating Supply Voltage: 3.3|5 V
• Data Bus Width: 8 Bit
• Program Memory Type: Flash
• Number Of Programmable I/os: 48
• Interface Type: SPI/TWI/USART/USB
• On-chip Adc: 8-chx10-bit
• Operating Temperature: -40 to 85 °C
• Number Of Timers: 4
• Lead Free Status / Rohs Status: Details

6.5.1
6.6
7593K–AVR–11/09
External Clock
Oscillator Calibration Register – OSCCAL
Table 6-8.
Note:
• 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 ±10% 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.
The device can utilize a external clock source as shown in
external clock, the CKSEL Fuses must be programmed as shown in
Bit
Read/Write
Initial Value
Power Conditions
BOD enabled
Fast rising power
Slowly rising power
1. The device is shipped with this option selected.
Start-up times for the internal calibrated RC Oscillator clock selection
7
CAL7
R/W
Device Specific Calibration Value
6
CAL6
R/W
Start-up Time from Power-
down and Power-save
5
CAL5
R/W
Reserved
6 CK
6 CK
6 CK
4
CAL4
R/W
3
CAL3
R/W
2
CAL2
R/W
Figure
Additional Delay from
Reset (V
14CK + 65 ms
14CK + 4.1 ms
AT90USB64/128
6-3. To run the device on an
Table
1
CAL1
R/W
14CK
CC
= 5.0V)
6-1.
(1)
0
CAL0
R/W
SUT1..0
OSCCAL
01
10
11
00
45