H8-3857 Datasheet, PDF (121/560 Pages) Renesas Technology Corp – 8-Bit Single-Chip Microcomputer

4. Clock Pulse Generators
Figure 4.8 shows the equivalent circuit of the 32.768-kHz crystal oscillator.
C_S
L_S
X₁
R_S
X₂
C₀
C₀ = 1.5 pF typ
R_S = 14 kΩ typ
f W = 32.768 kHz
Crystal oscillator: MX38T
(Nihon Denpa Kogyo)
Figure 4.8 Equivalent Circuit of 32.768-kHz Crystal Oscillator
Inputting an External Clock
• Circuit configuration
An external clock is input to the X₁ pin. The X₂ pin should be left open.
An example of the connection in this case is shown in figure 4.9.
External clock input
X₁
X₂
Open
Figure 4.9 Example of Connection when Inputting an External Clock
• External clock
Input a square waveform to the X1 pin. When using the CPU, timer A, timer C*, or an LCD,
with a subclock (φw) clock selected, do not stop the clock supply to the X₁ pin.
Note: * This is a function of the H8/3857 Group only, and is not provided in the H8/3854
Group.
Rev.3.00 Jul. 19, 2007 page 97 of 532
REJ09B0397-0300