Rev. 1.0, 02/00, page 179 of 1141
External Clock: The external clock signal should have the same frequency as the system clock
(
φ
).
Table 9.3 and figure 9.6 show the input conditions for the external clock.
Table 9.3
External Clock Input Conditions
V
CC
= 4.0 to 5.5 V
Item
Symbol
Min
Max
Unit
Test Conditions
External clock input low
pulse width
t
EXL
40
ns
External clock input high
pulse width
t
EXH
40
ns
External clock rise time
t
EXr
10
ns
External clock fall time
t
EXf
10
ns
Figure 9.6
t
EXH
t
EXL
t
EXr
t
EXf
OSC1
Figure 9.6 External Clock Input Timing
Table 9.4 shows the external clock output settling delay time, and figure 9.7 shows the external
clock output settling delay timing. The oscillator and duty adjustment circuit have a function for
adjusting the waveform of the external clock input at the OSC1 pin. When the prescribed clock
signal is input at the OSC1 pin, internal clock signal output is fixed after the elapse of the external
clock output settling delay time (t
DEXT
). As the clock signal output is not fixed during the t
DEXT
period, the reset signal should be driven low to maintain the reset state.