MPC555
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MPC556
CLOCKS AND POWER CONTROL
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
8-31
8.12.2 PLL, Low-Power, and Reset-Control Register (PLPRCR)
The PLL, low-power, and reset-control register (PLPRCR) is a 32-bit register powered
by the keep alive power supply.
24
—
Reserved
25:27
DFNL
Division factor low frequency. The user can load these bits with the desired divide value and
the CSRC bit to change the frequency. Changing the value of these bits does not result in a
loss of lock condition. These bits are cleared by power-on or hard reset. Refer to
for details on using these bits.
000 = Divide by 2
001 = Divide by 4
010 = Divide by 8
011 = Divide by 16
100 = Divide by 32
101 = Divide by 64
110 = Reserved
111 = Divide by 256
28
—
Reserved
29:31
DFNH
Division factor high frequency. These bits determine the general system clock frequency dur-
ing normal mode. Changing the value of these bits does not result in a loss of lock condition.
These bits are cleared by power-on or hard reset. The user can load these bits at any time
to change the general system clock rate. Note that the GCLKs generated by this division fac-
tor are not 50% duty cycle (i.e. CLKOUT).
000 = Divide by 1
001 = Divide by 2
010 = Divide by 4
011 = Divide by 8
100 = Divide by 16
101 = Divide by 32
110 = Divide by 64
111 = Reserved
Table 8-9 SCCR Bit Descriptions (Continued)
Bit(s)
Name
Description
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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