70592C Datasheet, PDF (129/314 Pages) Microchip Technology – High-Performance, 16-bit Microcontrollers

PIC24HJXXXGPX06A/X08A/X10A
For example, suppose a 10 MHz crystal is being used,
with “XT with PLL” being the selected oscillator mode.
If PLLPRE<4:0> = 0, then N1 = 2. This yields a VCO
input of 10/2 = 5 MHz, which is within the acceptable
range of 0.8-8 MHz. If PLLDIV<8:0> = 0x1E, then
M = 32. This yields a VCO output of 5 x 32 = 160 MHz,
which is within the 100-200 MHz ranged needed.
If PLLPOST<1:0> = 0, then N2 = 2. This provides a
Fosc of 160/2 = 80 MHz. The resultant device operating
speed is 80/2 = 40 MIPS.
EQUATION 9-3: XT WITH PLL MODE
EXAMPLE
FCY
=
F_----O_----S_---C_--
2
=
12-- _{⎝⎛ -1--0---0---0---20----0-⋅--0---0-2---}⋅_{------3---2-⎠⎞}
=
40 MIPS
FIGURE 9-2:
PIC24HJXXXGPX06A/X08A/X10A PLL BLOCK DIAGRAM
0.8-8.0 MHz
Here⁽¹⁾
Source (Crystal, External Clock
or Internal RC)
PLLPRE
X
N1
Divide by
2-33
FVCO
100-200 MHz
Here⁽¹⁾
12.5-80 MHz
Here⁽¹⁾
VCO
PLLPOST
FOSC
PLLDIV
M
Divide by
2-513
N2
Divide by
2, 4, 8
Note 1: This frequency range must be satisfied at all times.
TABLE 9-1: CONFIGURATION BIT VALUES FOR CLOCK SELECTION
Oscillator Mode
Oscillator Source POSCMD<1:0>
FNOSC<2:0>
Fast RC Oscillator with Divide-by-N
Internal
xx
111
(FRCDIVN)
Fast RC Oscillator with Divide-by-16
Internal
xx
110
(FRCDIV16)
Low-Power RC Oscillator (LPRC)
Internal
xx
101
Secondary (Timer1) Oscillator (SOSC)
Secondary
xx
100
Primary Oscillator (HS) with PLL
Primary
10
011
(HSPLL)
Primary Oscillator (XT) with PLL
Primary
01
011
(XTPLL)
Primary Oscillator (EC) with PLL
Primary
00
011
(ECPLL)
Primary Oscillator (HS)
Primary
10
010
Primary Oscillator (XT)
Primary
01
010
Primary Oscillator (EC)
Primary
00
010
Fast RC Oscillator with PLL (FRCPLL)
Internal
xx
001
Fast RC Oscillator (FRC)
Internal
xx
000
Note 1: OSC2 pin function is determined by the OSCIOFNC Configuration bit.
2: This is the default oscillator mode for an unprogrammed (erased) device.
See Note
1, 2
1
1
1
—
—
1
—
—
1
1
1
© 2011 Microchip Technology Inc.
DS70592C-page 129