MC908QT1 FREESCALE [Freescale Semiconductor, Inc], MC908QT1 Datasheet - Page 92

• Manufacturer Part Number: MC908QT1
• Description: Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Oscillator Module (OSC)
11.3.3 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 in the port A pullup enable register 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:
92
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 crystal manufacturer’s
data for more information.
1
FROM SIM
Note 1.
R
data. See
MCU
S
SIMOSCEN
can be zero (shorted) when used with higher-frequency crystals. Refer to manufacturer’s
S
Figure 11-2. XTAL Oscillator External Connections
1
(optional)
2
B
(can also be a fixed capacitor)
OSC1
Chapter 16 Electrical Specifications
MC68HC908QY/QT Family Data Sheet, Rev. 5
C
1
S
) is included in the diagram to follow strict Pierce
R
X
B
1
XTALCLK
NOTE
BUSCLKX4
OSC2
R
C
S
(1)
2
for component value recommendations.
TO SIM
BUSCLKX2
÷ 2
TO SIM
Freescale Semiconductor