Microchip Technology ARD00385 Data Sheet
2009-2011 Microchip Technology Inc.
DS39957D-page 43
PIC18F87K90 FAMILY
3.2
Control Registers
The OSCCON register (
) controls the main
aspects of the device clock’s operation. It selects the
oscillator type to be used, which of the power-managed
modes to invoke and the output frequency of the
INTOSC source. It also provides status on the oscillators.
oscillator type to be used, which of the power-managed
modes to invoke and the output frequency of the
INTOSC source. It also provides status on the oscillators.
The OSCTUNE register (
) controls the
tuning and operation of the internal oscillator block. It also
implements the PLLEN bit which controls the operation of
the Phase Locked Loop (PLL) (see
implements the PLLEN bit which controls the operation of
the Phase Locked Loop (PLL) (see
).
REGISTER 3-1:
OSCCON: OSCILLATOR CONTROL REGISTER
R/W-0
R/W-1
R/W-1
R/W-0
R
)
R-0
R/W-0
R/W-0
IDLEN
IRCF2
IRCF1
IRCF0
(
OSTS
HFIOFS
SCS1
)
SCS0
bit 7
bit 0
Legend:
R = Readable bit
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
x = Bit is unknown
bit 7
IDLEN:
Idle Enable bit
1
= Device enters an Idle mode when a SLEEP instruction is executed
0
= Device enters Sleep mode when a SLEEP instruction is executed
bit 6-4
IRCF<2:0>:
Internal Oscillator Frequency Select bits
(
111
= HF-INTOSC output frequency is used (16 MHz)
110
= HF-INTOSC/2 output frequency is used (8 MHz, default)
101
= HF-INTOSC/4 output frequency is used (4 MHz)
100
= HF-INTOSC/8 output frequency is used (2 MHz)
011
= HF-INTOSC/16 output frequency is used (1 MHz)
If INTSRC = 0 and MFIOSEL = 0:
)
010
= HF-INTOSC/32 output frequency is used (500 kHz)
001
= HF-INTOSC/64 output frequency is used (250 kHz)
000
= LF-INTOSC output frequency is used (31.25 kHz)
If INTSRC = 1 and MFIOSEL = 0:
)
010
= HF-INTOSC/32 output frequency is used (500 kHz)
001
= HF-INTOSC/64 output frequency is used (250 kHz)
000
= HF-INTOSC/512 output frequency is used (31.25 kHz)
If INTSRC = 0 and MFIOSEL = 1:
)
010
= MF-INTOSC output frequency is used (500 kHz)
001
= MF-INTOSC/2 output frequency is used (250 kHz)
000
= LF-INTOSC output frequency is used (31.25 kHz)
If INTSRC = 1 and MFIOSEL = 1:
)
010
= MF-INTOSC output frequency is used (500 kHz)
001
= MF-INTOSC/2 output frequency is used (250 kHz)
000
= MF-INTOSC/16 output frequency is used (31.25 kHz)
bit 3
OSTS:
Oscillator Start-up Timer Time-out Status bit
(
)
1
= Oscillator Start-up Timer (OST) time-out has expired: primary oscillator is running as defined by
OSC<3:0>
0
= Oscillator Start-up Timer (OST) time-out is running: primary oscillator is not ready; device is
running from an internal oscillator (HF-INTOSC, MF-INTOSC or LF-INTOSC)
Note 1:
Reset state depends on the state of the IESO Configuration bit (CONFIG1H<7>).
2:
Modifying these bits will cause an immediate clock frequency switch if the internal oscillator is providing
the device clocks.
the device clocks.
3:
Source selected by the INTSRC bit (OSCTUNE<7>).
4:
Modifying these bits will cause an immediate clock source switch.
5:
INTSRC = OSCTUNE<7> and MFIOSEL = OSCCON2<0>.