GMS81C2020 Datasheet, PDF (49/92 Pages) Hynix Semiconductor – CMOS Single-Chip 8-Bit Microcontroller with A/D Converter & VFD Driver

Hyundai Micro Electronics
GMS81C2020/GMS81C2120
cillator, as shown in Figure 13-2 .
SXO
C1
C2
SXI
Vss
Recommended: C1, C2 = 20pF±4pF for Crystals
Figure 13-3 Sub Oscillator Connections
To drive the device from an external clock source, XO
should be left unconnected while XI is driven as shown in
Figure 13-4 . There are no requirements on the duty cycle
of the external clock signal, since the input to the internal
clocking circuitry is through a divide-by-two flip-flop, but
minimum and maximum high and low times specified on
the data sheet must be observed.
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.
OPEN
XO
External
Clock
XI
Source
Vss
Oscillation circuit is designed to be used either with a ex-
ternal RC oscillator. Since External RC oscillator has their
own characteristic, the user should figure out the appropri-
ate value of external resister. (Please refer the DC Spec)
XO
REXT
XI
Vss
Figure 13-4 External R Connection
Note: When using a system clock oscillator, carry out wir-
ing in the broken line area in Figure 13-2 to prevent
any effects from wiring capacities.
- Minimize the wiring length.
- Do not allow wiring to intersect with other signal
conductors.
- Do not allow wiring to come near changing high
current.
- Set the potential of the grounding position of the
oscillator capacitor to that of VSS. Do not ground to
any ground pattern where high current is present.
- Do not fetch signals from the oscillator.
Nov. 1999 Ver 0.0
preliminary
49