Motorola NXP SYMPHONY DSP56007 Technical Data Manual page 10

Signal/Connection Descriptions
Clock and PLL signals
CLOCK AND PLL SIGNALS
Note: While the PLL on this DSP is identical to the PLL described in the DSP56000
Family Manual , two of the signals have not been implemented externally.
Specifically, there is no PLOCK signal or CKOUT signal available. Therefore,
the internal clock is not directly accessible and there is no external indication
that the PLL is locked. These signals were omitted to reduce the number of
pins and allow this DSP to be put in a smaller, less expensive package.
Signal Signal
Name Type
EXTAL Input
PCAP Input
PINIT Input
1-4
Freescale Semiconductor, Inc.
Table 1-4 Clock and PLL Signals
State
during
Reset
Input External Clock/Crystal—This input should be connected to an
external clock source. If the PLL is enabled, this signal is
internally connected to the on-chip PLL. The PLL can multiply
the frequency on the EXTAL pin to generate the internal DSP
clock. The PLL output is divided by two to produce a four-phase
instruction cycle clock, with the minimum instruction time being
two PLL output clock periods. If the PLL is disabled, EXTAL is
divided by two to produce the four-phase instruction cycle clock.
Input PLL Filter Capacitor—This input is used to connect a high-
quality (high "Q" factor) external capacitor needed for the PLL
filter. The capacitor should be as close as possible to the DSP with
heavy, short traces connecting one terminal of the capacitor to
PCAP and the other terminal to V
value is specified in
Note: When short lock time is critical, low dielectric absorption
capacitors such as polystyrene, polypropylene, or teflon are
recommended.
If the PLL is not used (i.e., it remains disabled at all times), there is
no need to connect a capacitor to the PCAP pin. It may remain
unconnected, or be tied to either V
Input PLL Initialization (PINIT)—During the assertion of hardware
reset, the value on the PINIT line is written into the PEN bit of the
PCTL register. When set, the PEN bit enables the PLL by causing
it to derive the internal clocks from the PLL voltage controlled
oscillator output. When the bit is cleared, the PLL is disabled and
the DSP's internal clocks are derived from the clock connected to
the EXTAL signal. After hardware RESET is deasserted, the
PINIT signal is ignored.
DSP56007/D
For More Information On This Product,
Go to: www.freescale.com
Signal Description
. The required capacitor
CCP
Table 2-6 on page 2-6.
or GND.
cc
MOTOROLA