PIC24HJ16GP304-E Datasheet, PDF (91/274 Pages) Microchip Technology – High-Performance, 16-bit Microcontrollers

PIC24HJ32GP202/204 AND PIC24HJ16GP304
For a primary oscillator or FRC oscillator, output ‘FIN’,
the PLL output ‘FOSC’ is given by:
EQUATION 8-2: FOSC CALCULATION
FOSC = FIN ⋅
⎛
⎝
N^-----1----M⋅^------N^{----2--⎠⎞}
For example, when 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 MHz to 200 MHz range, which is 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 8-3: XT WITH PLL MODE
EXAMPLE
FCY =
F_----O_----S_---C_--
2
=
1--
2
⋅
⎛
⎝
1---0----0---0--0-2--0--_{⋅-0---0--2---}⋅_{------3---2-⎠⎞}
=
40
MIPS
FIGURE 8-2:
PIC24HJ32GP202/204 AND PIC24HJ16GP304 PLL BLOCK DIAGRAM
0.8-8.0 MHz⁽¹⁾
FVCO
100-200 MHz⁽¹⁾
12.5-80 MHz⁽¹⁾
Source (Crystal, External Clock
or Internal RC)
PLLPRE
X
VCO
N1
Divide by
2-33
PLLDIV
M
Divide by
2-513
Note 1: This frequency range must be satisfied at all times.
PLLPOST
N2
Divide by
2, 4, 8
FOSC
TABLE 8-1: CONFIGURATION BIT VALUES FOR CLOCK SELECTION
Oscillator Mode
Oscillator Source POSCMD<1:0>
Fast RC Oscillator with Divide-by-N
Internal
xx
(FRCDIVN)
Fast RC Oscillator with Divide-by-16
Internal
xx
(FRCDIV16)
Low-Power RC Oscillator (LPRC)
Internal
xx
Secondary (Timer1) Oscillator (SOSC)
Secondary
xx
Primary Oscillator (HS) with PLL
Primary
10
(HSPLL)
Primary Oscillator (XT) with PLL
Primary
01
(XTPLL)
Primary Oscillator (EC) with PLL
Primary
00
(ECPLL)
Primary Oscillator (HS)
Primary
10
Primary Oscillator (XT)
Primary
01
Primary Oscillator (EC)
Primary
00
Fast RC Oscillator with PLL (FRCPLL)
Internal
xx
Fast RC Oscillator (FRC)
Internal
xx
Note 1: OSC2 pin function is determined by the OSCIOFNC Configuration bit.
2: This is the default oscillator mode for an unprogrammed (erased) device.
FNOSC<2:0>
111
110
101
100
011
011
011
010
010
010
001
000
See Note
1, 2
1
1
1
—
—
1
—
—
1
1
1
© 2007-2011 Microchip Technology Inc.
DS70289H-page 91