Datasheet

CKSEL 3..0 SUT1..0 Start-up time from power-down
and power-save
Additional delay from reset
(VCC = 5.0V)
0101 Ext Osc
00 1K CK 14CK
01 1K CK 14CK + 4ms
10 16K CK 14CK + 4ms
11 16K CK 14CK + 64ms
0001 Ext Clk
00 6 CK
(1)
14CK
01 6 CK
(1)
14CK + 4ms
10 6 CK
(1)
14CK + 64ms
Reserved
Note: This value do not provide a proper restart; do not use PD in this clock scheme.
Figure 9-3. PCK clocking system

8 MHz
RC OS CILLATOR
OSCCAL
XTAL1
XTAL2
OSCILLATORS
DIVIDE
BY 8
DIVIDE
BY 2
CK
PLL
64x
PLLE
Lock
Dete ctor
PLOCK
SOURCE
PLLF
DIVIDE
BY 4
CLK
PLL
9.7. 128kHz Internal Oscillator
The 128kHz internal oscillator is a low power oscillator providing a clock of 128kHz. The frequency is
nominal at 3V and 25°C. This clock is used by the Watchdog Oscillator.
9.8. External Clock
To drive the device from an external clock source, XTAL1 should be driven as shown below. To run the
device on an external clock, the CKSEL Fuses must be programmed to “0000”.
Figure 9-4. External Clock Drive Configuration

XTAL2
XTAL1
GND
NC
Exte rna l
Clock
Signa l
Atmel ATmega16M1/32M1/64M1 [DATASHEET]
Atmel-8209F-ATmega16M1/32M1/64M1_Datasheet_Complete-10/2016
53