PIC16F7X7
4.5.1
INTRC MODES
4.5.2
OSCTUNE REGISTER
Using the internal oscillator as the clock source can
eliminate the need for up to two external oscillator pins,
after which it can be used for digital I/O. Two distinct
configurations are available:
The internal oscillator’s output has been calibrated at the
factory but can be adjusted in the application. This is
done by writing to the OSCTUNE register (Register 4-1).
The tuning sensitivity is constant throughout the tuning
range. The OSCTUNE register has a tuning range of
±12.5%.
• In INTIO1 mode, the OSC2 pin outputs FOSC/4,
while OSC1 functions as RA7 for digital input and
output.
When the OSCTUNE register is modified, the INTOSC
and INTRC frequencies will begin shifting to the new
frequency. The INTRC clock will reach the new
frequency within 8 clock cycles (approximately
8 * 32 µs = 256 µs); the INTOSC clock will stabilize
within 1 ms. Code execution continues during this shift.
There is no indication that the shift has occurred. Oper-
ation of features that depend on the 31.25 kHz INTRC
clock source frequency, such as the WDT, Fail-Safe
Clock Monitor and peripherals, will also be affected by
the change in frequency.
• In INTIO2 mode, OSC1 functions as RA7 and
OSC2 functions as RA6, both for digital input and
output.
REGISTER 4-1:
OSCTUNE: OSCILLATOR TUNING REGISTER (ADDRESS 90h)
U-0
—
U-0
—
R/W-0
TUN5
R/W-0
TUN4
R/W-0
TUN3
R/W-0
TUN2
R/W-0
TUN1
R/W-0
TUN0
bit 7
bit 0
bit 7-6
bit 5-0
Unimplemented: Read as ‘0’
TUN<5:0>: Frequency Tuning bits
011111= Maximum frequency
011110=
•
•
•
000001=
000000= Center frequency. Oscillator module is running at the calibrated frequency.
111111=
•
•
•
100000= Minimum frequency
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
DS30498C-page 36
2004 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
