Section 18 Clock Pulse Generator
Rev. 3.00 Mar. 14, 2006 Page 666 of 804
REJ09B0104-0300
Table 18.2 Crystal Resonator Characteristics
Frequency
(MHz)
4 6 8 9
R
S
Max. (
Ω
) 120 100 80 80
C
0
Max. (pF)
7
7
7
7
18.2.2 External
Clock
Input
An external clock signal can be input as shown in the examples in figure 18.4. If the XTAL pin is
left open, make sure that parasitic capacitance is no more than 10 pF. When the counter clock is
input to the XTAL pin, make sure that the external clock is held high in standby mode.
EXTAL
XTAL
External clock input
Open
(a) XTAL pin left open
EXTAL
XTAL
External clock input
(b) Counter clock input on XTAL pin
Figure 18.4 External Clock Input (Examples)
For the input conditions of the external clock, refer to table 21.4, Clock Timing, in section 21.3.1,
Clock Timing. The input external clock should be from 4 to 9 MHz.
18.3 PLL
Circuit
The PLL circuit has the function of multiplying the frequency of the clock from the oscillator by a
factor of 8. The frequency multiplication factor is fixed.
18.4 Frequency
Divider
The frequency divider divides the PLL clock to generate a 1/2, 1/4, or 1/8 clock. After bits ICK2
to ICK0 and PCK 2 to PCK0 are modified, this LSI operates at the modified frequency.
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Содержание H8SX series
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