PIC24HJ12GP201 Datasheet, PDF (81/234 Pages) Microchip Technology – High-Performance, 16-Bit Microcontrollers

PIC24HJ12GP201/202
For a primary oscillator or FRC oscillator, output ‘FIN’,
the PLL output ‘FOSC’ is given by:
EQUATION 7-2: FOSC CALCULATION
( ) ^{FOSC = FIN*}
M
N1*N2
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 7-3: XT WITH PLL MODE
EXAMPLE
( ) FCY = FOSC = 1
22
10000000*32
2*2
= 40 MIPS
FIGURE 7-2:
PIC24HJ12GP201/202 PLL BLOCK DIAGRAM
0.8-8.0 MHz
Here
Source (Crystal, External Clock
or Internal RC)
PLLPRE
X
Divide by
2-33
100-200 MHz
Here
12.5-80 MHz
Here
VCO
PLLDIV
Divide by
2-513
PLLPOST
Divide by
2, 4, 8
FOSC
TABLE 7-1: 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 Oscillator (EC)
Primary
01
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 Microchip Technology Inc.
Preliminary
DS70282B-page 79