ATmega8(L)
External Clock
Figure 114. External Clock Drive Waveforms
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
1/tCLCL Oscillator Frequency
tCLCL
Min
0
Max
Min
0
Max
Units
8
16
MHz
Clock Period
High Time
Low Time
Rise Time
Fall Time
125
50
62.5
25
tCHCX
tCLCX
tCLCH
tCHCL
ns
50
25
1.6
1.6
0.5
0.5
s
Change in period from one
clock cycle to the next
2
2
ꢀ
tCLCL
Table 100. External RC Oscillator, Typical Frequencies
R [k](1)
C [pF]
22
f(2)
33
650kHz
2.0MHz
10
22
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
237
2486AA–AVR–02/2013
ATMEL [ ATMEL ]
