MC68HC705SR3 MOTOROLA [Motorola, Inc], MC68HC705SR3 Datasheet - Page 23

• Manufacturer Part Number: MC68HC705SR3
• Description: High-density Complementary Metal Oxide Semiconductor (HCMOS) Microcontroller Units
• Manufacturer: MOTOROLA [Motorola, Inc]

The external oscillator clock frequency, f
frequency, f
2.2.1
The circuit in Figure 2-1(a) shows a typical oscillator circuit for an AT-cut, parallel resonant crystal.
The crystal manufacturer’s recommendations should be followed, 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 external start-up resistor of
approximately 10M is needed between OSC1 and OSC2 for the crystal type oscillator.
2.2.2
An external clock from another CMOS-compatible device can be connected to the OSC1 input,
with the OSC2 input not connected, as shown in Figure 2-1(b).
MC68HC05SR3
(a) Crystal or ceramic resonator connections
(c) RC option 1 - external resistor
OP
.
Crystal Oscillator
External Clock
Freescale Semiconductor, Inc.
Unconnected
OSC1
OSC1
For More Information On This Product,
10% to 25% accurate
25p
10M
MCU
MCU
Go to: www.freescale.com
Figure 2-1 Oscillator Connections
OSC2
OSC2
25p
PIN DESCRIPTIONS
R
OSC
V
, is divided by two to produce the internal operating
DD
(b) External clock source connection
(d) RC option 2 - internal resistor
OSC1
OSC1
25% to 50% accurate
MCU
MCU
External Clock
OSC2
OSC2
Unconnected
MOTOROLA
TPG
2-3
2