Crystal Oscillator; External Crystal Oscillator Circuitexternal Clock Source; Connecting An External Clock Signal Using Xtal - Freescale Semiconductor 56F800 User Manual

4.5.3 Crystal Oscillator

The internal crystal oscillator circuit is designed to interface with a parallel-resonant crystal
resonator whose frequency range is optimized for 4MHz.
circuit. Follow the crystal supplier's recommendations when selecting a crystal, because crystal
parameters determine the 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
layout capacitances. The crystal and associated components should be mounted as close as
possible to the EXTAL and XTAL pins to minimize output distortion and start-up stabilization
time.
Figure 4-4. External Crystal Oscillator CircuitExternal Clock Source
The recommended method of connecting an external clock is provided in
external clock source is connected to XTAL while the EXTAL pin is held at V
Figure 4-5. Connecting an External Clock Signal using XTAL
Freescale Semiconductor
Crystal Frequency = 2–6MHz (optimized for 4MHz)
EXTAL XTAL
Sample External Crystal
R
Parameters:
z
R = 10 Megohms
z
DSP56F82x
XTAL
External
Clock
On-Chip Clock Synthesis (OCCS), Rev. 3
Figure 4-4 illustrates a typical crystal
EXTAL
V /2
DDA
Pin Descriptions
Figure 4-5. The
/2.
DDA
7