AT90USB1286-16MU ATMEL [ATMEL Corporation], AT90USB1286-16MU Datasheet - Page 46

• Manufacturer Part Number: AT90USB1286-16MU
• Description: Microcontroller with 64/128K Bytes of ISP Flash and USB Controller
• Manufacturer: ATMEL [ATMEL Corporation]

6.7
46
External Clock
AT90USB64/128
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 6-10.
The device can utilize a external clock source as shown in
external clock, the CKSEL Fuses must be programmed as shown in
Figure 6-3.
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table
Table 6-11.
When applying an external clock, it is required to avoid sudden changes in the applied clock fre-
quency to ensure stable operation of the MCU. A variation in frequency of more than 2% from
one clock cycle to the next can lead to unpredictable behavior. If changes of more than 2% is
required, ensure that the MCU is kept in Reset during the changes.
Note that the System Clock Prescaler can be used to implement run-time changes of the internal
clock frequency while still ensuring stable operation. Refer to
47
BOD enabled
Fast rising power
Slowly rising power
BOD enabled
Fast rising power
Slowly rising power
for details.
Power Conditions
Power Conditions
6-10.
6-11.
Start-up Times for the 128 kHz Internal Oscillator
External Clock Drive Configuration
Start-up Times for the External Clock Selection
EXTERNAL
Start-up Time from Power-
Start-up Time from Power-
down and Power-save
down and Power-save
SIGNAL
CLOCK
NC
Reserved
Reserved
6 CK
6 CK
6 CK
6 CK
6 CK
6 CK
XTAL2
XTAL1
GND
Additional Delay from
Additional Delay from
Reset (V
14CK + 4.1 ms
14CK + 64 ms
14CK + 65 ms
14CK + 4 ms
Figure
“System Clock Prescaler” on page
Reset
14CK
14CK
CC
6-3. To run the device on an
= 5.0V)
Table
6-1.
SUT1..0
SUT1..0
00
01
10
00
01
10
11
11
7593A–AVR–02/06