mc68hc908qb4 Freescale Semiconductor, Inc, mc68hc908qb4 Datasheet - Page 97

• Manufacturer Part Number: mc68hc908qb4
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

11.3.4 XTAL Oscillator
The XTAL oscillator circuit is designed for use with an external crystal or ceramic resonator to provide an
accurate clock source. In this configuration, the OSC2 pin is dedicated to the external crystal circuit. The
OSC2EN bit has no effect when this clock mode is selected.
In its typical configuration, the XTAL oscillator is connected in a Pierce oscillator configuration, as shown
in
represent actual circuitry.
The oscillator configuration uses five components:
Freescale Semiconductor
Figure
•
•
•
•
•
Crystal, X
Fixed capacitor, C
Tuning capacitor, C
Feedback resistor, R
Series resistor, R
11-2. This figure shows only the logical representation of the internal components and may not
The series resistor (R
oscillator guidelines and may not be required for all ranges of operation,
especially with high frequency crystals. Refer to the oscillator
characteristics table in the Electricals section for more information.
1
SIMOSCEN (INTERNAL SIGNAL) OR
OSCENINSTOP (BIT LOCATED IN
CONFIGURATION REGISTER)
MCU
S
Figure 11-2. XTAL Oscillator External Connections
1
(optional)
2
OSC1
B
(can also be a fixed capacitor)
C
1
S
MC68HC908QB8 Data Sheet, Rev. 2
) is included in the diagram to follow strict Pierce
R
X
B
1
XTALCLK
NOTE
OSC2
R
C
S
2
BUSCLKX4
See the electrical section for details.
÷ 2
BUSCLKX2
Functional Description
97