MC68HC08JB1 Datasheet, PDF (73/216 Pages) Motorola, Inc – Microcontrollers

The series resistor (R_S) is included in the diagram to follow strict Pierce
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.
7.4 I/O Signals
The following paragraphs describe the oscillator input/output (I/O)
signals.
7.4.1 Crystal Amplifier Input Pin (OSC1)
The OSC1 pin is an input to the crystal oscillator amplifier.
7.4.2 Crystal Amplifier Output Pin (OSC2)
The OSC2 pin is the output of the crystal oscillator inverting amplifier.
7.4.3 Oscillator Enable Signal (SIMOSCEN)
The SIMOSCEN signal comes from the system integration module (SIM)
and enables the oscillator.
7.4.4 External Clock Source (OSCXCLK)
The crystal oscillator output signal passes through the clock doubler and
OSCXCLK is the output signal of the clock doubler. OSCXCLK runs at
twice the speed of the crystal (f_XCLK). Figure 7-1 shows only the logical
relation of OSCXCLK to OSC1 and 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 startup.
MC68HC08JB1 — Rev. 2.1
Freescale Semiconductor
Technical Data
73