HMS81C2012A Datasheet, PDF (86/107 Pages) List of Unclassifed Manufacturers – CMOS Single-Chip 8-Bit Microcontroller with A/D Converter & VFD Driver

HMS81C2012A/2020A
18. OSCILLATOR CIRCUIT
The HMS81C20xxA has two oscillation circuits internal-
ly. X_IN and X_OUT are input and output for main frequency
and SX_IN and SX_OUT are input and output for sub frequen-
cy, respectively, inverting amplifier which can be config-
ured for being used as an on-chip oscillator, as shown in
Figure 18-1.
C1
X_OUT
C1
SX_OUT
C2
4.19MHz
X_IN
V_SS
C2
32.768KHz ^SXIN
V_SS
Recommend
Crystal Oscillator
Ceramic Resonator
C1,C2 = 20pF
C1,C2 = 30pF
Recommend
C1,C2 = 100~120pF
Crystal or Ceramic Oscillator
Open
External Clock
X_OUT
X_IN
R_EXT
X_OUT
For selection R value,
X_IN
Refer to AC Characteristics
External Oscillator
RC Oscillator (mask option)
Figure 18-1 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.
Oscillation circuit is designed to be used either with a ce-
ramic resonator or crystal oscillator. Since each crystal and
X_OUT
ceramic resonator have their own characteristics, the user
X_IN
should consult the crystal manufacturer for appropriate
values of external components.
In addition, see Figure 18-2 for the layout of the crystal.
Note: Minimize the wiring length. Do not allow the wiring to
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 18-2 Layout of Oscillator PCB circuit
82
SEP. 2004 Ver 2.00