GMS81C5108 Datasheet, PDF (83/102 Pages) Hynix Semiconductor – HYNIX SEMICONDUCTOR INC. 8-BIT SINGLE-CHIP MICROCONTROLLERS

GMS81C5108
21. OSCILLATOR CIRCUIT
The GMS81C5108 has two oscillation circuits internally.
X_IN and X_OUT are input and output for main frequency and
SX_IN and SX_OUT are input and output for sub frequency,
respectively, inverting amplifier which can be configured
for being used as an on-chip oscillator, as shown in Figure
21-1.
C1
X_OUT
C3
SX_OUT
C2
4.19MHz
X_IN
V_SS
C4
32.768KHz ^SXIN
V_SS
Recommend
Crystal Oscillator
Ceramic Resonator
C1,C2 = 20pF
C1,C2 = 20pF
Recommend
C3,C4 = 30pF
Crystal or Ceramic Oscillator
Open
External Clock
X_OUT
X_IN
R_EXT
X_OUT
Select R value according to AC Characteristics.
The Cap. is built in(5pF).
X_IN
External Oscillator
RC Oscillator
Figure 21-1 Oscillation Circuit
Oscillation circuit is designed to be used either with a ce-
ramic resonator or crystal oscillator. Since each crystal and
ceramic resonator have their own characteristics, the user
should consult the crystal manufacturer for appropriate
values of external components.
In addition, see Figure 21-2 for the layout of the crystal.
X_OUT
Note: Minimize the wiring length. Do not allow the wiring to
X_IN
intersect with other signal conductors. Do not allow the wir-
ing to come near changing high current. Set the potential of
the grounding position of the oscillator capacitor to that of
VSS. Do not ground it to any ground pattern where high cur-
rent is present. Do not fetch signals from the oscillator.
Figure 21-2 Layout of Oscillator PCB circuit
80
JUNE 2001 Ver 1.0