PIC24HJ12GP201_11 Datasheet, PDF (89/262 Pages) Microchip Technology – High-Performance, 16-bit Microcontrollers 5-cycle latency

PIC24HJ12GP201/202
EQUATION 8-2: FOSC CALCULATION
FOSC = FIN ⋅
⎛
⎝
N^-----1----M⋅^------N^{----2--⎠⎞}
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 8-3: 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 8-2:
PIC24HJ12GP201/202 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 8-1: CONFIGURATION BIT VALUES FOR CLOCK SELECTION
Oscillator Mode
Oscillator
Source
POSCMD<1:0>
Fast RC Oscillator with Divide-by-N (FRCDIVN)
Internal
xx
Fast RC Oscillator with Divide-by-16 (FRCDIV16)
Internal
xx
Low-Power RC Oscillator (LPRC)
Internal
xx
Secondary (Timer1) Oscillator (SOSC)
Secondary
xx
Primary Oscillator (HS) with PLL (HSPLL)
Primary
10
Primary Oscillator (XT) with PLL (XTPLL)
Primary
01
Primary Oscillator (EC) with PLL (ECPLL)
Primary
00
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
Note
1, 2
1
1
1
—
—
1
—
—
1
1
1
© 2007-2011 Microchip Technology Inc.
DS70282E-page 89