MC80F0204 Datasheet, PDF (42/126 Pages) List of Unclassifed Manufacturers – 8-BIT SINGLE-CHIP MICROCONTROLLERS

MC80F0104/0204
Preliminary
n addition, see Figure 10-3 for the layout of the crystal.
omitted for more cost saving. However, the characteristics
of external R only oscillation are more variable than exter-
nal RC oscillation.
X_OUT
X_IN
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.
OPEN
Xout
External
Clock
Xin
Source
Vss
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
Vdd
R_EXT
C_EXT
f_XIN÷4
X_IN
Cint ≈ 6pF
X_OUT
Figure 10-5 RC Oscillator Connections
V_DD
R_EXT
f_XIN÷4
X_IN
C_INT ≈ 6pF
X_OUT
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
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Mar. 2005 Ver 0.2