MPC563XM Reference Manual, Rev. 1
558
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
Bypass mode with crystal reference is the default mode at reset if the PLLREF input is driven high. After
reset, this mode can be entered by programming ESYNCR1[PLLCFG] as shown in
.
17.2.3.2
Bypass Mode with External Reference
The bypass mode with external reference functions the same as bypass mode with crystal reference, except
that the system clock is driven by an external clock generator connected to the EXTAL pin, rather than a
crystal oscillator. The input frequency range is the same and frequency modulation is not available.
Bypass mode with external reference is the default mode at reset if the PLLREF input is driven low. After
reset, this mode can be entered by programming ESYNCR1[PLLCFG] as shown in
.
17.2.3.3
Normal Mode with Crystal Reference
In the normal mode with crystal reference, the FMPLL receives an input clock frequency from the crystal
oscillator and the pre-divider, and multiplies the frequency to create the FMPLL output clock. The user
must supply a crystal that is within the appropriate frequency range, the crystal manufacturer
recommended external support circuitry, and short signal route from the MCU to the crystal.
In normal mode with crystal reference, the FMPLL can generate a frequency modulated clock or a
non-modulated clock (locked on a single frequency). The modulation rate, modulation depth, output
divider (RFD) and whether the FMPLL is modulating or not can be programmed by writing to the FMPLL
registers.
17.2.3.4
Normal Mode with External Reference
The normal mode with external reference functions the same as normal mode with crystal reference,
except that the input clock reference to the FMPLL is driven by an external clock generator connected to
the EXTAL pin, rather than a crystal oscillator. The input frequency range is the same and frequency
modulation is available.
17.3
External Signal Description
lists external signals used by the FMPLL during normal operation.
17.3.1
Detailed Signal Descriptions
describes the external signals used by the FMPLL.
Table 17-3. Signal Properties
Name
Function
I/O
Pull
PLLREF
Configures the FMPLL clock reference at reset
I/O
Up
XTAL
Output drive for external crystal
O
—
EXTAL_EXTCLK
Crystal/external clock input
I/O
—
VDDPLL
Analog power supply (1.2V +/- 10%)
Power
—
VSSPLL
Analog ground
Ground
—