user manual

General Description
General Release Specification MC68HC05RC16 — Rev. 3.0
24 General Description MOTOROLA
1.5.3 OSC1 and OSC2
These pins provide control input for an on-chip clock oscillator circuit. A
crystal, a ceramic resonator, or an external signal connects to these pins
to provide a system clock. The oscillator frequency is two times the
internal bus rate.
Figure 1-5 shows the recommended circuit when using a crystal. The
crystal and components should be mounted as close as possible to the
input pins to minimize output distortion and startup stabilization time.
A ceramic resonator may be used in place of the crystal in cost-sensitive
applications. Figure 1-5 (a) shows the recommended circuit for using a
ceramic resonator. The manufacturer of the particular ceramic resonator
being considered should be consulted for specific information.
An external clock should be applied to the OSC1 input with the OSC2 pin
not connected (see Figure 1-5 (b)). This setup can be used if the user
does not want to run the CPU with a crystal.
Figure 1-5. Oscillator Connections
<
OSC1 OSC2OSC1 OSC2
MCUMCU
EXTERNAL CLOCK
UNCONNECTED
(a) Crystal/Ceramic Resonator (b) External Clock Source
10 MΩ
Oscillator Connections Connections
30 pF
30 pF