ATA8741 ATMEL Corporation, ATA8741 Datasheet - Page 46

• Manufacturer Part Number: ATA8741
• Manufacturer: ATMEL Corporation

46
ATA8741
Figure 14-3. External Clock Drive Configuration
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table 14-8 on page
Table 14-8.
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. It is required to ensure that the
MCU is kept in Reset during such changes in the clock frequency.
Note that the System Clock Prescaler can be used to implement run-time changes of the internal
clock frequency while still ensuring stable operation. See to
47
SUT1..0
for details.
00
01
10
11
Power-down and Power-save
Start-up Times for the External Clock Selection
Start-up Time from
46.
6 CK
6 CK
6 CK
EXTERNAL
SIGNAL
CLOCK
Additional Delay from
Reserved
14CK + 64 ms
14CK + 4 ms
CLKI
GND
Reset
14CK
“System Clock Prescaler” on page
Fast rising power
BOD enabled
Slowly rising power
Recommended Usage
9140B–INDCO–07/09