HD64F2149 Datasheet, PDF (739/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

Avoid
Signal A Signal B
C_L2
The chip
XTAL
EXTAL
C_L1
Figure 23.4 Example of Incorrect Board Design
23.3.2 External Clock Input
Circuit Configuration: An external clock signal can be input as shown in the examples in figure
23.5. If the XTAL pin is left open, make sure that stray capacitance is no more than 10 pF.
In example (b), make sure that the external clock is held high in standby mode, subactive mode,
subsleep mode, and watch mode.
EXTAL
XTAL
Open
External clock input
(a) XTAL pin left open
EXTAL
XTAL
External clock input
(b) Complementary clock input at XTAL pin
Figure 23.5 External Clock Input (Examples)
External Clock: The external clock signal should have the same frequency as the system clock
(ø).
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