HD64F3644PV Datasheet, PDF (107/551 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

Section 4 Clock Pulse Generators
Figure 4.8 shows the equivalent circuit of the 32.768-kHz crystal resonator.
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 resonator:MX38T
(Nihon Denpa Kogyo)
Figure 4.8 Equivalent Circuit of 32.768-kHz Crystal Resonator
Pin Connection when Not Using Subclock: When the subclock is not used, connect pin X₁ to
V_CC and leave pin X₂ open, as shown in figure 4.9.
V_CC
X₁
X₂
Open
Figure 4.9 Pin Connection when not Using Subclock
4.4 Prescalers
The H8/3644 Group is equipped with two on-chip prescalers having different input clocks
(prescaler S and prescaler W). Prescaler S is a 13-bit counter using the system clock (φ) as its
input clock. Its prescaled outputs provide internal clock signals for on-chip peripheral modules.
Prescaler W is a 5-bit counter using a 32.768-kHz signal divided by 4 (φ_W/4) as its input clock. Its
prescaled outputs are used by timer A as a time base for timekeeping.
Prescaler S (PSS): Prescaler S is a 13-bit counter using the system clock (φ) as its input clock. It
is incremented once per clock period.
Prescaler S is initialized to H'0000 by a reset, and starts counting on exit from the reset state.
Rev. 6.00 Sep 12, 2006 page 85 of 526
REJ09B0326-0600