PIC18F47J53 Datasheet, PDF (43/586 Pages) Microchip Technology – 28/44-Pin, High-Performance USB Microcontrollers with nanoWatt XLP Technology

PIC18F47J53 FAMILY
The use of the flag and control bits in the OSCCON
register is discussed in more detail in Section 4.0
“Low-Power Modes”.
Note 1: The Timer1 crystal driver is enabled by
setting the T1OSCEN bit in the Timer1
Control register (T1CON<3>). If the
Timer1 oscillator is not enabled, then any
attempt to select the Timer1 clock source
will be ignored, unless the CONFIG2L
register’s T1DIG bit is set.
2: If Timer1 is driving a crystal, it is recom-
mended that the Timer1 oscillator be
operating and stable prior to switching to
it as the clock source; otherwise, a very
long delay may occur while the Timer1
oscillator starts.
3.5.2 OSCILLATOR TRANSITIONS
PIC18F47J53 family devices contain circuitry to
prevent clock “glitches” when switching between clock
sources. A short pause in the device clock occurs dur-
ing the clock switch. The length of this pause is the sum
of two cycles of the old clock source and three to four
cycles of the new clock source. This formula assumes
that the new clock source is stable.
Clock transitions are discussed in more detail in
Section 4.1.2 “Entering Power-Managed Modes”.
REGISTER 3-2: OSCCON: OSCILLATOR CONTROL REGISTER (ACCESS FD3h)
R/W-0
IDLEN
bit 7
R/W-1
IRCF2
R/W-1
IRCF1
R/W-0
IRCF0
R-1⁽¹⁾
OSTS
R-0
FLTS
R/W-0
SCS1
R/W-0
SCS0
bit 0
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
x = Bit is unknown
bit 7
bit 6-4
bit 3
bit 2
bit 1-0
IDLEN: Idle Enable bit
1 = Device enters Idle mode on SLEEP instruction
0 = Device enters Sleep mode on SLEEP instruction
IRCF<2:0>: Internal Oscillator Frequency Select bits
111 = 8 MHz (INTOSC drives clock directly)
110 = 4 MHz⁽²⁾
101 = 2 MHz
100 = 1 MHz
011 = 500 kHz
010 = 250 kHz
001 = 125 kHz
000 = 31 kHz (from either INTOSC/256 or INTRC directly)⁽³⁾
OSTS: Oscillator Start-up Time-out Status bit⁽¹⁾
1 = Oscillator Start-up Timer time-out has expired; primary oscillator is running
0 = Oscillator Start-up Timer time-out is running; primary oscillator is not ready
FLTS: Frequency Lock Tuning Status bit
1 = INTOSC is stable
0 = INTOSC is not stable
SCS<1:0>: System Clock Select bits
11 = Postscaled internal clock (INTRC/INTOSC derived)
10 = Reserved
01 = Timer1 oscillator
00 = Primary clock source (INTOSC postscaler output when FOSC<2:0> = 001 or 000)
00 = Primary clock source (CPU divider output for other values of FOSC<2:0>)
Note 1: Reset value is ‘0’ when Two-Speed Start-up is enabled and ‘1’ if disabled.
2: Default output frequency of INTOSC on Reset (4 MHz).
3: Source selected by the INTSRC bit (OSCTUNE<7>).
 2010 Microchip Technology Inc.
Preliminary
DS39964B-page 43