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Section 4 Clock Pulse Generators
• H8/38347 Group and H8/38447 Group
Connect pin X
to GND and leave pin X
1
EXCL in register PMR2 to 1 to supply the external clock to the internal components of the device.
A connection example is shown in figure 4.9 (b).
P3
/UD/EXCL
1
Figure 4.9 (b) Pin Connection when Inputting External Clock
Frequency
Duty
4. Notes on H8/38347 and H8/38447
In the H8/38347 and H8/38447 the subclock oscillator input pin is controlled by the EXCL bit in
the PMR2 register. When EXCL is cleared to 0 the X1 pin (resonator connection only) is used,
and when EXCL is set to 1 the EXCL pin (external clock only) is used. Caution is necessary when
switching from the H8/3847R to a program. Writing 1 to bit 7 in PMR2 (empty bit with initial
value 1 on H8/3847R) selects EXCL as the input pin, so no subclock is supplied internally even if
a resonator is connected. Furthermore, P31 becomes unusable. To prevent this it is necessary to
change the program so that 0 is written to the EXCL bit.
Rev. 6.00 Aug 04, 2006 page 124 of 680
REJ09B0145-0600
open. Input an external clock to pin EXCL. Set bit
2
X
1
GND
X
Open
2
(H8/38347 Group and H8/38447 Group)
External clock input
Subclock (φ φ φ φ w)
45% to 55%
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