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Signal Descriptions
MC68360 USER’S MANUAL
is the general system clock. CLKO2 is 2
× CLKO1 if the on-chip clock synthesizer PLL is
used, and is 1
× CLKO1 otherwise.
2.1.10.2 CRYSTAL OSCILLATOR (EXTAL, XTAL). These two pins are the connections
for an external crystal to the internal oscillator circuit. If an external oscillator is used, it
should be connected to EXTAL, with XTAL left open.
2.1.10.3 EXTERNAL FILTER CAPACITOR (XFC). This pin is used to add an external
capacitor to the filter circuit of the PLL. The capacitor should be connected between XFC
and VCCSYN.
2.1.10.4 CLOCK MODE SELECT (MODCK1–MODCK0). The state of these active-high
input signals during reset selects the type of external clock that is used by the PLL in the
clock synthesizer to generate the system clocks.
Table 2-5 lists the default values of the
PLL.
1This mode is reserved.
2.1.11 Instrumentation and Emulation Signals
These signals are used for test or software debugging. Refer to Section 5 CPU32+ for more
information on these signals.
2.1.11.1 INSTRUCTION FETCH/DEVELOPMENT SERIAL INPUT (IFETCH/DSI). This
active-low output signal indicates when the CPU32+ is performing an instruction word
prefetch and when the instruction pipeline has been flushed. Additionally, this signal is the
serial input to the CPU32+ in its background debug mode to issue background commands,
etc.
2.1.11.2 INSTRUCTION PIPE/DEVELOPMENT SERIAL OUTPUT (IPIPE0/DSO). This
active-low output signal is used to track movement of words through the instruction pipeline.
Additionally, this signal is the serial output from the CPU32+ in its background debug mode
to issue background status, etc.
2.1.11.3 INSTRUCTION PIPE/ROW ADDRESS SELECT DOUBLE-DRIVE (IPIPE1/
RAS1DD). This active-low output signal is used to track movement of words through the
instruction pipeline. This signal also functions as a second output of the RAS1 signal to
increase fanout capability.
2.1.11.4 BREAKPOINT/DEVELOPMENT SERIAL CLOCK (BKPT/DSCLK). This
active-
low input signal is used to signal a hardware breakpoint to the CPU32+. Additionally, this
Table 2-5. Default Operation Mode of the PLL
MODCK
1–0
PLL
Prescaled by
128
Multi. Factor
(MF + 1)
EXTAL Freq.
(examples)
CLKIN to the
PLL
Initial Freq.
(VCO/2)
001
Disabled
Reserved
01
Enabled
No
1
>10 MHz
=EXTAL
10
Enabled
Yes
401
4.192 MHz
32.75 kHz
13.14 MHz
11
Enabled
No
401
32.768 kHz
13.14 MHz
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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