Freescale Semiconductor MC68HC08KH12, Datasheet

Page: 99 / 262

MC68HC(7)08KH12
—
Rev. 1.1 Advance Information
Freescale Semiconductor
99
8.5.6 Buffered Crystal Clock Output (CGMVOUT)
CGMVOUT buffers the OSC1 clock for external use.
8.5.7 CGMVSEL
CGMVSEL must be tied low or floated.
8.5.8 Oscillator Enable Signal (SIMOSCEN)
The SIMOSCEN signal comes from the system integration module (SIM)
and enables the oscillator and PLL.
8.5.9 Crystal Output Frequency Signal (CGMXCLK)
CGMXCLK is the crystal oscillator output signal. It runs at the full speed
of the crystal (f
XCLK
) and comes directly from the crystal oscillator circuit.
Figure 8-2 shows only the logical relation of CGMXCLK to OSC1 and
OSC2 and may not represent the actual circuitry. The duty cycle of
CGMXCLK is unknown and may depend on the crystal and other
external factors. Also, the frequency and amplitude of CGMXCLK can be
unstable at startup.
8.5.10 CGM Base Clock Output (CGMOUT)
CGMOUT is the clock output of the CGM. This signal goes to the SIM,
which generates the MCU clocks. CGMOUT is a 50 percent duty cycle
clock running at twice the bus frequency. CGMOUT is software
programmable to be either the oscillator output, CGMXCLK, divided by
two or the VCO clock, CGMVCLK, divided by two.
8.5.11 CGM CPU Interrupt (CGMINT)
CGMINT is the interrupt signal generated by the PLL lock detector.