
337
8272E–AVR–04/2013
ATmega164A/PA/324A/PA/644A/PA/1284/P
28.3
Clock characteristics
Notes:
1. Voltage range for Atmel ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P.
28.3.1
External clock drive waveforms
Figure 28-2. External clock drive waveforms.
28.3.2
External clock drive
Table 28-10. Calibration accuracy of internal RC oscillator.
Frequency
V
CC
Temperature
Calibration accuracy
Factory calibration
8.0MHz
3V
25
C±10%
User calibration
7.3 - 8.1MHz
-40
C - 85C±1%
VIL1
VIH1
Table 28-11. External clock drive.
Symbol
Parameter
VCC = 1.8 - 5.5V
VCC = 2.7 - 5.5V
VCC = 4.5 - 5.5V
Units
Min.
Max.
Min.
Max.
Min.
Max.
1/tCLCL
Oscillator Frequency
0
4
0
10
0
20
MHz
tCLCL
Clock Period
250
100
50
ns
tCHCX
High Time
100
40
20
tCLCX
Low Time
100
40
20
tCLCH
Rise Time
2.0
1.6
0.5
s
tCHCL
Fall Time
2.0
1.6
0.5
t
CLCL
Change in period from one
clock cycle to the next
22
2
%