
dsPIC30F3014/4013
DS70138G-page 144
2010 Microchip Technology Inc.
20.2
Oscillator Configurations
20.2.1
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<2:0> Configuration bits that select one of
four oscillator groups,
b)
and FPR<4:0> Configuration bits that select one
of 13 oscillator choices within the primary group.
20.2.2
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, XT, XTL and HS Oscillator
modes (upon wake-up from Sleep, POR and BOR) for
the primary oscillator.
TABLE 20-2:
CONFIGURATION BIT VALUES FOR CLOCK SELECTION
Oscillator Mode
Oscillator
Source
FOS<2:0>
FPR<4:0>
OSC2
Function
ECIO w/PLL 4x
PLL
1
10
1
0
1
I/O
ECIO w/PLL 8x
PLL
1
10
1
0
I/O
ECIO w/PLL 16x
PLL
1
10
1
I/O
FRC w/PLL 4x
PLL
1
10
0
1
I/O
FRC w/PLL 8x
PLL
1
10
1
0
1
0
I/O
FRC w/PLL 16x
PLL
1
10
0
1
I/O
XT w/PLL 4x
PLL
1
10
0
1
0
1
OSC2
XT w/PLL 8x
PLL
1
10
0
1
0
OSC2
XT w/PLL 16x
PLL
1
10
0
1
OSC2
HS2 w/PLL 4x
PLL
1
11
0
1
OSC2
HS2 w/PLL 8x
PLL
1
11
0
1
0
OSC2
HS2 w/PLL 16x
PLL
1
11
0
1
OSC2
HS3 w/PLL 4x
PLL
1
11
0
1
0
1
OSC2
HS3 w/PLL 8x
PLL
1
11
0
1
0
OSC2
HS3 w/PLL 16x
PLL
1
11
0
1
OSC2
ECIO
External
0
1
10
1
0
I/O
XT
External
0
1
10
0
1
0
OSC2
HS
External
0
1
10
0
1
0
OSC2
EXT
External
0
1
10
1
0
1
CLKO
ERC
External
0
1
10
1
0
1
CLKO
ERCIO
External
0
1
10
1
0
I/O
XTL
External
0
1
10
0
OSC2
LP
Secondary
0
0X
X
(Notes 1, 2)
FRC
Internal FRC
0
1X
X
(Notes 1, 2)
LPRC
Internal LPRC
0
1
0X
X
(Notes 1, 2)
Note 1:
The OSC2 pin is either usable as a general purpose I/O pin functionality only depending on the Primary
Oscillator mode selection (FPR<4:0>).
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.