DSPIC30F6010-20I Datasheet, PDF (144/222 Pages) Microchip Technology – dsPIC30F6010 Data Sheet

dsPIC30F6010
21.2 Oscillator Configurations
21.2.1 INITIAL CLOCK SOURCE
SELECTION
While coming out of Power-on Reset or Brown-out
Reset, the device selects its clock source based on:
a) FOS<1:0> Configuration bits that select one of
four oscillator groups.
b) AND FPR<3:0> Configuration bits that select
one of 13 oscillator choices within the primary
group.
The selection is as shown in Table 21-2.
TABLE 21-2: CONFIGURATION BIT VALUES FOR CLOCK SELECTION
Oscillator Mode
Oscillator
Source
FOS1 FOS0 FPR3 FPR2 FPR1 FPR0
OSC2
Function
EC
Primary
1
1
1
0
1
1
ECIO
Primary
1
1
1
1
0
0
EC w/ PLL 4x
Primary
1
1
1
1
0
1
EC w/ PLL 8x
Primary
1
1
1
1
1
0
EC w/ PLL 16x
Primary
1
1
1
1
1
1
ERC
Primary
1
1
1
0
0
1
ERCIO
Primary
1
1
1
0
0
0
XT
Primary
1
1
0
1
0
0
XT w/ PLL 4x
Primary
1
1
0
1
0
1
XT w/ PLL 8x
Primary
1
1
0
1
1
0
XT w/ PLL 16x
Primary
1
1
0
1
1
1
XTL
Primary
1
1
0
0
0
X
HS
Primary
1
1
0
0
1
X
LP
Secondary
0
0
—
—
—
—
FRC
Internal FRC
0
1
—
—
—
—
LPRC
Internal LPRC
1
0
—
—
—
—
Note 1: OSC2 pin function is determined by the Primary Oscillator mode selection (FPR<3:0>).
CLKO
I/O
I/O
I/O
I/O
CLKO
I/O
OSC2
OSC2
OSC2
OSC2
OSC2
OSC2
(Notes 1, 2)
(Notes 1, 2)
(Notes 1, 2)
2: Note that OSC1 pin cannot be used as an I/O pin, even if the secondary oscillator or an internal clock
source is selected at all times.
21.2.2 OSCILLATOR START-UP TIMER
(OST)
In order to ensure that a crystal oscillator (or ceramic
resonator) has started and stabilized, an oscillator
start-up timer is included. It is a simple 10-bit counter
that counts 1024 TOSC cycles before releasing the
oscillator clock to the rest of the system. The time-out
period is designated as TOST. The TOST time is involved
every time the oscillator has to restart (i.e., on POR,
BOR and wake-up from Sleep). The oscillator start-up
timer is applied to the LP Oscillator, XT, XTL, and HS
modes (upon wake-up from Sleep, POR and BOR) for
the primary oscillator.
21.2.3 LP OSCILLATOR CONTROL
Enabling the LP oscillator is controlled with two
elements:
1. The current oscillator group bits COSC<1:0>.
2. The LPOSCEN bit (OSCON register).
The LP oscillator is ON (even during Sleep mode) if
LPOSCEN = 1. The LP oscillator is the device clock if:
• COSC<1:0> = 00 (LP selected as main oscillator)
and
• LPOSCEN = 1
Keeping the LP oscillator ON at all times allows for a
fast switch to the 32 kHz system clock for lower power
operation. Returning to the faster main oscillator will
still require a start-up time.
DS70119E-page 142
© 2006 Microchip Technology Inc.