GMS81C1102 Datasheet, PDF (44/89 Pages) Hynix Semiconductor – 8-BIT SINGLE-CHIP MICROCONTROLLERS

GMS81C1102 / GMS81C1202
14. CLOCK GENERATOR
The clock generator produces the basic clock pulses which
provide the system clock to be supplied to the CPU and pe-
ripheral hardware. The main system clock oscillator oscillates
with a crystal resonator or a ceramic resonator connected to the
Xin and Xout pins. External clocks can be input to the main
system clock oscillator. In this case, input a clock signal to
the Xin pin and open the Xout pin

OSCILLATION ^fxin
CIRCUIT
CLOCK PULSE
GENERATOR
Internal system clock
STOP
WAKEUP
PRESCALER
÷1 ÷2 ÷4 ÷8 ÷16 ÷32 ÷64 ÷128 ÷256 ÷512 ÷1024 ÷2048
Peripheral clock
Figure 14-1 Block Diagram of Clock Pulse Generator
14.1 Oscillation Circuit
X_IN and X_OUT are the input and output, respectively, a in-
verting amplifier which can be set for use as an on-chip os-
cillator, as shown in Figure 14-2 .
Xout
C1
R1
C2
Xin
Vss
Recommended: C1, C2 = 30pF±10pF for Crystals
R1 = 1MΩ
Figure 14-2 Oscillator Connections
ings for timing insensitive applications. The RC
oscillator frequency is a function of the supply voltage, the
external resistor (Rext) and capacitor (Cext) values, and
the operating temperature.
The user needs to take into account variation due to toler-
ance of external R and C components used. Figure 14-4
shows how the RC combination is connected to the
GMS81C1202.
OPEN
Xout
External
Clock
Xin
Source
Vss
To drive the device from an external clock source, Xout
should be left unconnected while Xin is driven as shown in
Figure 14-3. 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
In addition, the GMS81C1202 has an ability for the exter-
nal RC oscillated operation. It offers additional cost sav-
Figure 14-3 External Clock Connections
Note: When using a system clock oscillator, carry out wir-
ing in the broken line area in Figure 14-2 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.
Jan. 2002 ver 2.0
41