ATMEGA8_08 Datasheet, PDF (244/308 Pages) ATMEL Corporation – 8-bit with 8K Bytes In-System Programmable Flash

External Clock
Figure 114. External Clock Drive Waveforms
Drive Waveforms
V_IH1
V_IL1
External Clock
Drive
Table 99. External Clock Drive
Symbol
1/t_CLCL
t_CLCL
t_CHCX
t_CLCX
t_CLCH
t_CHCL
Δt_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
ns
ns
μs
μs
2
2
%
Table 100. External RC Oscillator, Typical Frequencies
R [kΩ]⁽¹⁾
C [pF]
f⁽²⁾
33
22
650 kHz
Notes:
10
22
2.0 MHz
1. R should be in the range 3 kΩ - 100 kΩ, and C should be at least 20 pF. 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.
244 ATmega8(L)
2486T–AVR–05/08