Datasheet

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
Table 9-11 on page 37.
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 9-13.
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 10
(1)
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