ATmega8(L)
External Clock Drive
Waveforms
Figure 114. External Clock Drive Waveforms
VIH1
VIL1
External Clock Drive
Table 99. External Clock Drive
VCC = 2.7V to 5.5V VCC = 4.5V to 5.5V
Symbol Parameter
Min
0
Max
Min
0
Max
Units
MHz
ns
1/tCLCL
tCLCL
tCHCX
tCLCX
tCLCH
tCHCL
Oscillator Frequency
8
16
Clock Period
High Time
Low Time
Rise Time
Fall Time
125
50
62.5
25
ns
50
25
ns
1.6
1.6
0.5
0.5
µs
µs
Change in period from one
clock cycle to the next
2
2
%
∆tCLCL
Table 100. External RC Oscillator, Typical Frequencies
R [kΩ](1)
C [pF]
47
f(2)
100
87 kHz
650 kHz
2.0 MHz
33
22
10
22
Notes: 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.
239
2486M–AVR–12/03
ATMEL [ ATMEL ]
