GMS87C1102 datasheet(44/89 Pages) HYNIX

44 / 89 page

GMS81C1102 / GMS81C1202

Jan. 2002 ver 2.0

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

Figure 14-1 Block Diagram of Clock Pulse Generator

14.1 Oscillation Circuit

XIN and XOUT 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 .

Figure 14-2 Oscillator Connections

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-

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.

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.

Internal system clock

PRESCALER

CLOCK PULSE

÷1

Peripheral clock

÷2

÷4

÷8

÷16

÷128 ÷256 ÷512 ÷1024

÷32

÷64

GENERATOR

÷2048

STOP

WAKEUP

fxin

OSCILLATION

CIRCUIT

Xout

Xin

Vss

Recommended: C1, C2 = 30pF±10pF for Crystals

R1 = 1M

Ω

Xout

Xin

Vss

OPEN

External

Clock

Source

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