ATMEGA8_14 Datasheet, PDF (237/331 Pages) ATMEL Corporation – High-performance, Low-power Atmel

External Clock
Figure 114. External Clock Drive Waveforms
Drive Waveforms
V_IH1
V_IL1
ATmega8(L)
External Clock
Drive
Table 99. External Clock Drive
Symbol
1/t_CLCL
t_CLCL
t_CHCX
t_CLCX
t_CLCH
t_CHCL
t_CLCL
Parameter
Oscillator Frequency
Clock Period
High Time
Low Time
Rise Time
Fall Time
Change in period from one
clock cycle to the next
V_CC = 2.7V to 5.5V
Min
Max
0
8
125
50
50
1.6
1.6
V_CC = 4.5V to 5.5V
Min
Max
0
16
62.5
25
25
0.5
0.5
Units
MHz
ns
s
2
2
%
Table 100. External RC Oscillator, Typical Frequencies
R [k]⁽¹⁾
C [pF]
f⁽²⁾
33
22
650kHz
10
22
2.0MHz
Notes: 1. R should be in the range 3k - 100k, and C should be at least 20pF. The C values given in
the table includes pin capacitance. This will vary with package type
2. The frequency will vary with package type and board layout
2486AA–AVR–02/2013
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