s908qc16vdse Freescale Semiconductor, Inc, s908qc16vdse Datasheet - Page 97

• Manufacturer Part Number: s908qc16vdse
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 10
Oscillator Mode (OSC)
10.1 Introduction
The oscillator (OSC) module is used to provide a stable clock source for the MCU system and bus.
The OSC shares its pins with general-purpose input/output (I/O) port pins. See
location of these shared pins. The OSC2EN bit is located in the port A pull enable register (PTAPUEN)
on this MCU. See
10.2 Features
The bus clock frequency is one fourth of any of these clock source options:
10.3 Functional Description
The oscillator contains these major subsystems:
10.3.1 Internal Signal Definitions
The following signals and clocks are used in the functional description and figures of the OSC module.
10.3.1.1 Oscillator Enable Signal (SIMOSCEN)
The SIMOSCEN signal comes from the system integration module (SIM) and disables the XTAL oscillator
circuit, the RC oscillator, or the internal oscillator in stop mode. OSCENINSTOP in the configuration
register can be used to override this signal.
Freescale Semiconductor
1. Internal oscillator: An internally generated, fixed frequency clock, trimmable to ± 0.4%. There are
2. External oscillator: An external clock that can be driven directly into OSC1.
3. External RC: A built-in oscillator module (RC oscillator) that requires an external R connection only.
4. External crystal: A built-in XTAL oscillator that requires an external crystal or ceramic-resonator.
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four choices for the internal oscillator, 25.6 MHz, 12.8 MHz, 8 MHz, or 4 MHz. The 4-MHz internal
oscillator is the default option out of reset.
The capacitor is internal to the chip.
There are three crystal frequency ranges supported, 8–32 MHz, 1–8 MHz, and 32–100 kHz.
Internal oscillator circuit
Internal or external clock switch control
External clock circuit
External crystal circuit
External RC clock circuit
Chapter 11 Input/Output Ports (PORTS)
MC68HC908QC16 • MC68HC908QC8 • MC68HC908QC4 Data Sheet, Rev. 4
for information on PTAPUEN register.
Figure 10-1
for port
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