July 16, 1999
GENERAL RELEASE SPECIFICATION
MC68HC05J5A
REV 2.1
GENERAL DESCRIPTION
MOTOROLA
1-5
1.
2.
3.
A crystal as shown in
A ceramic resonator as shown in
An external clock signal as shown in
The frequency, f
OSC
, of the oscillator or external clock source is divided by two to
produce the internal operating frequency, f
Figure 1-3
(a)
Figure 1-3
Figure 1-3
(a)
(b)
OP
.
Crystal Oscillator
The circuit in
resonant crystal. The crystal manufacturer’s recommendations should be fol-
lowed, as the crystal parameters determine the external component values
required to provide maximum stability and reliable start-up. The load capacitance
values used in the oscillator circuit design should include all stray capacitances.
The crystal and components should be mounted as close as possible to the pins
for start-up stabilization and to minimize output distortion. An internal start-up
resistor is provided between OSC1 and OSC2/R for the crystal type oscillator.
Figure 1-3
(a) shows a typical oscillator circuit for an AT-cut, parallel
Figure 1-3. Oscillator Connections
Ceramic Resonator Oscillator
In cost-sensitive applications, a ceramic resonator can be used in place of the
crystal. The circuit in
Figure 1-3
(a) can be used for a ceramic resonator. The res-
onator manufacturer’s recommendations should be followed, as the resonator
parameters determine the external component values required for maximum sta-
bility and reliable starting. The load capacitance values used in the oscillator cir-
cuit design should include all stray capacitances. The ceramic resonator and
components should be mounted as close as possible to the pins for start-up stabi-
lization and to minimize output distortion. An internal start-up resistor is provided
between OSC1 and OSC2/R for the ceramic resonator type oscillator.
External Clock
An external clock from another CMOS-compatible device can be connected to the
OSC1 input, with the OSC2/R input not connected, as shown in
Figure 1-3
(b).
MCU
37pF
OSC1
OSC2/R
37 pF
R
OSC
unconnected
External Clock
OSC1
OSC2/R
MCU
(a) Crystal or ceramic
resonator connection
(b) External clock source
connection
R
OSC
: see Section 11. Electrical Specifications.
F
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
.