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Clock Module
8-12
Freescale Semiconductor
8.3.5
Clock Operation During Reset
This section describes the PLL reset operation. Power-on reset and normal reset are described.
8.3.5.1
Power-On Reset (POR)
After VDD_PLL and the input clock are within specification, the PLL is held in reset for at least ten input
clock cycles to initialize the PLL. The reset configuration signals are used to select the multiply factor of
the PLL and the reset state of the PLL registers. While in reset, the PLL input clock is output to the device.
After RESET de-asserts, PLL output clocks generate; however, until the PSR[LOCK] bit is set, the PLL
output clock frequencies are not stable and within specification. When this bit is set, the PLL is in
frequency lock.
8.3.5.2
External Reset
When RESET asserts, the PLL input clock outputs to the device, and the PLL does not begin acquiring
lock until RESET is negated. The PSR[LOCK] bit is cleared and remains cleared while the PLL is
acquiring lock.
CAUTION
When running in an unlocked state, the clocks the PLL generate are not
guaranteed to be stable and may exceed the maximum specified frequency.
Содержание MCF54455
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