MC68HC908JK1 Datasheet, PDF (98/210 Pages) Motorola, Inc – MC68HC908JK1

Oscillator (OSC)
8.5 I/O Signals
The following paragraphs describe the oscillator I/O signals.
8.5.1 Crystal Amplifier Input Pin (OSC1)
OSC1 pin is an input to the crystal oscillator amplifier or the input to the
RC oscillator circuit.
8.5.2 Crystal Amplifier Output Pin (OSC2/PTA6/RCCLK)
For the X-tal oscillator device, OSC2 pin is the output of the crystal
oscillator inverting amplifier.
For the RC oscillator device, OSC2 pin can be configured as a general
purpose I/O pin PTA6, or the output of the internal RC oscillator clock,
RCCLK.
Option
X-tal oscillator
RC oscillator
OSC2 pin function
Inverting OSC1
Controlled by PTAEN bit in PTAPUER ($0D)
PTA6EN = 0: RCCLK output
PTA6EN = 1: PTA6 I/O
8.5.3 Oscillator Enable Signal (SIMOSCEN)
The SIMOSCEN signal comes from the system integration module (SIM)
and enables/disables the X-tal oscillator circuit or the RC-oscillator.
8.5.4 X-tal Oscillator Clock (XTALCLK)
XTALCLK is the X-tal oscillator output signal. It runs at the full speed of
the crystal (f_XCLK) and comes directly from the crystal oscillator circuit.
Figure 8-1 shows only the logical relation of XTALCLK to OSC1 and
OSC2 and may not represent the actual circuitry. The duty cycle of
XTALCLK is unknown and may depend on the crystal and other external
factors. Also, the frequency and amplitude of XTALCLK can be unstable
at start-up.
Technical Data
98
Oscillator (OSC)
MC68H(R)C908JL3 — Rev. 1.0
MOTOROLA