mc68hc908bd48 Freescale Semiconductor, Inc, mc68hc908bd48 Datasheet - Page 113

• Manufacturer Part Number: mc68hc908bd48
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

8.4 I/O Signals
8.4.1 Crystal Amplifier Input Pin (OSC1)
8.4.2 Crystal Amplifier Output Pin (OSC2)
8.4.3 Oscillator Enable Signal (SIMOSCEN)
8.4.4 External Clock Source (OSCXCLK)
8.4.5 Oscillator Out (OSCOUT)
MC68HC908BD48
Freescale Semiconductor
—
Rev. 2.1
The following paragraphs describe the oscillator I/O signals.
The OSC1 pin is an input to the crystal oscillator amplifier.
An externally generated clock also can feed the OSC1 pin of the crystal
oscillator circuit. Connect the external clock to the OSC1 pin and let the
OSC2 pin float.
The OSC2 pin is the output of the crystal oscillator inverting amplifier.
The SIMOSCEN signal comes from the SIM and enables the oscillator.
OSCXCLK is the crystal oscillator output signal. It runs at the full speed
of the crystal (f
Figure 8-1
OSC2 and may not represent the actual circuitry. The duty cycle of
OSCXCLK is unknown and may depend on the crystal and other
external factors. Also, the frequency and amplitude of OSCXCLK can be
unstable at start-up.
The clock driven to the SIM is the crystal frequency divided by two. This
signal is driven to the SIM for generation of the bus clocks used by the
CPU and other modules on the MCU. OSCOUT will be divided again in
the SIM and results in the internal bus frequency being one fourth of the
OSCXCLK frequency.
shows only the logical relation of OSCXCLK to OSC1 and
XCLK
Oscillator (OSC)
) and comes directly from the crystal oscillator circuit.
Oscillator (OSC)
Data Sheet
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