MagnaChip MC80F0104, User Manual, Page: 42 / 126

MC80F0104/0204 Preliminary
38 Mar. 2005 Ver 0.2
n addition, see Figure 10-3 for the layout of the crystal.
Figure 10-3 Layout of Oscillator PCB circuit
To drive the device from an external clock source, Xout
should be left unconnected while Xin is driven as shown in
Figure 10-4 . 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.
Figure 10-4 External Clock Connections
In addition, the MC80F0104/0204 has an ability for the ex-
ternal 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 (R
EXT
) and capacitor (C
EXT
) 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 10-5 shows how the RC combination is connected
to the MC80F0104/0204. External capacitor (C
EXT
) can be
omitted for more cost saving. However, the characteristics
of external R only oscillation are more variable than exter-
nal RC oscillation.
Figure 10-5 RC Oscillator Connections
Figure 10-6 R Oscillator Connections
To use the RC oscillation , the CLK option of the configu-
ration bits (20FF
H
) should be set to “EXRC or EXRCXO”.
The oscillator frequency, divided by 4, is output from the
Xout pin, and can be used for test purpose or to synchro-
nize other logic.
In addition to external crystal/resonator and external RC/R
oscillation, the MC80F0104/0204 provides the internal
4MHz or 2MHz oscillation. The internal 4MHz/2MHz os-
cillation needs no external parts.
To use the internal 4MHz/2MHz oscillation, the CLK op-
tion of the configuration bits should be set to “IN4MCLK”,
“IN2MCLK”, “IN4MCLKXO” or “IN2MCLKXO”. For
detail description on the configuration bits, refer to "23.
Device Configuration Area" on page 102
X
OUT
X
IN
Xout
Xin
Vss
OPEN
External
Clock
Source
X
OUT
X
IN
Vdd
C
EXT
f
XIN
÷
4
R
EXT
Cint
≈
6pF
X
OUT
X
IN
V
DD
f
XIN
÷
4
R
EXT
C
INT
≈
6pF