ATMEGA2561V ATMEL [ATMEL Corporation], ATMEGA2561V Datasheet - Page 45

• Manufacturer Part Number: ATMEGA2561V
• Description: 8-bit Microcontroller with 64K/128K/256K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

128 kHz Internal
Oscillator
External Clock
2549K–AVR–01/07
Table 18. Start-up times for the internal calibrated RC Oscillator clock selection
Note:
The 128 kHz internal Oscillator is a low power Oscillator providing a clock of 128 kHz.
The frequency is nominal at 3V and 25°C. This clock may be select as the system clock
by programming the CKSEL Fuses to “11” as shown in Table 19.
Table 19. 128 kHz Internal Oscillator Operating Modes
Note:
When this clock source is selected, start-up times are determined by the SUT Fuses as
shown in Table 20.
Table 20. Start-up Times for the 128 kHz Internal Oscillator
To drive the device from an external clock source, XTAL1 should be driven as shown in
Figure 23. To run the device on an external clock, the CKSEL Fuses must be pro-
grammed to “0000”.
Figure 23. External Clock Drive Configuration
Power Conditions
BOD enabled
Fast rising power
Slowly rising power
BOD enabled
Fast rising power
Slowly rising power
Power Conditions
1. The device is shipped with this option selected.
1. The frequency is preliminary value. Actual value is TBD.
Nominal Frequency
EXTERNAL
128 kHz
ATmega640/1280/1281/2560/2561
SIGNAL
Start-up Time from Power-
Start-up Time from Power-
CLOCK
down and Power-save
down and Power-save
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 + 65 ms
14CK + 4.1 ms
14CK + 64 ms
14CK + 4 ms
Reset
14CK
14CK
CC
CKSEL3:0
= 5.0V)
0011
(1)
SUT1:0
SUT1:0
00
01
10
11
01
11
00
10
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