37
8272E–AVR–04/2013
ATmega164A/PA/324A/PA/644A/PA/1284/P
When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in
Note:
1.
The device is shipped with this option selected.
9.7
128kHz internal oscillator
The 128kHz internal Oscillator is a low power Oscillator providing a clock of 128kHz. The fre-
quency is nominal at 3V and 25
C. This clock may be select as the system clock by
programming the CKSEL Fuses to “0011” as shown in
Table 9-12.
Note:
1. Note that the 128kHz oscillator is a very low power clock source, and is not designed for high
accuracy.
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in
Table 9-11.
Start-up times for the Internal Calibrated RC Oscillator clock selection.
Power conditions
Start-up time from power-
down and power-save
Additional delay from
reset (V
CC = 5.0V)
SUT1..0
BOD enabled
6CK
14CK
00
Fast rising power
6CK
14CK + 4.1ms
01
Slowly rising power
6CK
14CK + 65ms
Reserved
11
Table 9-12.
128kHz Internal Oscillator Operating Modes
(2).Nominal frequency
CKSEL3..0
128kHz
0011
Table 9-13.
Start-up times for the 128kHz internal oscillator.
Power conditions
Start-up time from power-
down and power-save
Additional delay from
reset
SUT1..0
BOD enabled
6CK
14CK
00
Fast rising power
6CK
14CK + 4ms
01
Slowly rising power
6CK
14CK + 64ms
10
Reserved
11