
584
Table 16-4 External Clock Input Conditions
Item
Symbol
Min
Max
Unit
Test Conditions
External clock input lowpulse width
t
EXL
25
—
ns
Figure 16-6
External clock input high pulse width tEXH
25
—
ns
External clock rise time
t
EXr
—
6.25
ns
External clock fall time
t
EXf
—
6.25
ns
Clock low pulse width level
t
CL
0.4
0.6
t
cyc
≥ 5 MHz Figure 18-3
80
—
ns
< 5 MHz
Clock high pulse width level
t
CH
0.4
0.6
t
cyc
≥ 5 MHz
80
—
ns
< 5 MHz
The external clock input conditions when the duty adjustment circuit is not used are shown in table
16-5 and figure 16-6. When the duty adjustment circuit is not used, the output waveform
depends on the external clock input waveform, and so no restrictions apply.
Table 16-5 External Clock Input Conditions when the Duty Adjustment Circuit is not Used
Item
Symbol
Min
Max
Unit
Test Conditions
External clock input low pulse width
t
EXL
31.25
—
ns
Figure 16-6
External clock input high pulse width t
EXH
31.25
—
ns
External clock rise time
t
EXr
—
6.25
ns
External clock fall time
t
EXf
—
6.25
ns
Note:
When duty adjustment circuit is not used, the maximum frequency decreases according to
the input waveform. (Example: When t
EXL = tEXH = 50 ns, and tEXr = tEXf = 10 ns, clock cycle
time = 120 ns; therefore, maximum operating frequency = 8.3 MHz)
tEXH
tEXL
tEXr
tEXf
VCC × 0.5
EXTAL
Figure 16-6 External Clock Input Timing