PIC18F45J10 Datasheet, PDF (27/358 Pages) Microchip Technology – 28/40/44-Pin High-Performance RISC Microcontrollers with nanoWatt Technology

PIC18F45J10 FAMILY
2.4 PLL Frequency Multiplier
A Phase Locked Loop (PLL) circuit is provided as an
option for users who want to use a lower frequency
oscillator circuit, or to clock the device up to its highest
rated frequency from a crystal oscillator. This may be
useful for customers who are concerned with EMI due
to high-frequency crystals, or users who require higher
clock speeds from an internal oscillator. For these
reasons, the HSPLL and ECPLL modes are available.
The HSPLL and ECPLL modes provide the ability to
selectively run the device at 4 times the external oscil-
lating source to produce frequencies up to 40 MHz.
The PLL is enabled by setting the PLLEN bit in the
OSCTUNE register (Register 2-1).
FIGURE 2-4:
PLL BLOCK DIAGRAM
HSPLL or ECPLL (CONFIG2L)
PLL Enable (OSCTUNE)
OSC2
HS or EC
OSC1 Mode
FIN
FOUT
Phase
Comparator
Loop
Filter
÷4
VCO
SYSCLK
REGISTER 2-1: OSCTUNE: PLL CONTROL REGISTER
U-0
R/W-0⁽¹⁾
U-0
U-0
U-0
U-0
U-0
U-0
—
PLLEN⁽¹⁾
—
—
—
—
—
—
bit 7
bit 0
bit 7
bit 6
bit 5-0
Unimplemented: Read as ‘0’
PLLEN: Frequency Multiplier PLL Enable bit⁽¹⁾
1 = PLL enabled
0 = PLL disabled
Note 1: Available only for ECPLL and HSPLL oscillator configurations; otherwise, this bit is
unavailable and read as ‘0’.
Unimplemented: Read as ‘0’
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared x = Bit is unknown
© 2007 Microchip Technology Inc.
Preliminary
DS39682C-page 25