Datasheet

dsPIC30F6011/6012/6013/6014
DS70117F-page 148 © 2006 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<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 20-2.
TABLE 20-2: CONFIGURATION BIT VALUES FOR CLOCK SELECTION
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 T
OSC cycles before releasing the
oscillator clock to the rest of the system. The time-out
period is designated as T
OST. 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.
20.2.3 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 oper-
ation. Returning to the faster main oscillator will still
require a start-up time.
Oscillator Mode
Oscillator
Source
FOS1 FOS0 FPR3 FPR2 FPR1 FPR0
OSC2
Function
EC Primary
1 11011 CLKO
ECIO Primary 1 11100 I/O
EC w/ PLL 4x Primary 1 11101 I/O
EC w/ PLL 8x Primary
1 11110 I/O
EC w/ PLL 16x Primary 1 11111 I/O
ERC Primary 1 11001 CLKO
ERCIO Primary
1 11000 I/O
XT Primary 1 10100 OSC2
XT w/ PLL 4x Primary 1 10101 OSC2
XT w/ PLL 8x Primary
1 10110 OSC2
XT w/ PLL 16x Primary 1 10111 OSC2
XTL Primary 1 1000X OSC2
HS Primary
1 1001X OSC2
LP Secondary 0 0 ————(Notes 1, 2)
FRC Internal FRC 0 1 ————(Notes 1, 2)
LPRC Internal LPRC
1 0 ————(Notes 1, 2)
Note 1: OSC2 pin function is determined by the Primary Oscillator mode selection (FPR<3:0>).
2: 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.