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The external clock/crystal (EXTAL) input provides two clock generation op-
tions. EXTAL may be used to interface the internal generator to an external
crystal (see Figure 3-7). Typical circuit parameters are C1=C2=25 pF and
R = 700 kD using a parallel resonant crystal.
EXTAL can also accept a CMOS-level clock input. The crystal output (XTAL)
connects the internal crystal generator output to an external crystal. If an
external clock is used, XTAL should be left unconnected. The CLKO pin, which
drives the high-speed system clock, may be used to synchronize other pe-
ripherals to the IMP system clock.
MC68302
EXTAL
C1
D
R
C2
XTAL
Figure 3-7. Using an External Crystal
EXTAL can also accept a CMOS-level clock input. The crystal output (XTAL)
connects the internal crystal generator output to an external crystal. If an
external clock is used, XTAL should be left unconnected. The CLKO pin, which
drives the high-speed system clock, may be used to synchronize other pe-
ripherals to the IMP system clock.
3.8 SYSTEM CONTROL
3-46
The IMP system control consists of an SCR that configures the following
functions:
• System Status and Control Logic
• Disable CPU (M68000) Logic
MC68302 USER'S MANUAL
MOTOROLA
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