PIC12F639 Microchip Technology, PIC12F639 Datasheet - Page 35

• Manufacturer Part Number: PIC12F639
• Description: (PIC12F635 / PIC12F636 / PIC12F639) 8/14-PIN FLASH-BASED / 8-BIT CMOS MICROCONTROLLERS WITH NANOWATT TECHNOLOGY
• Manufacturer: Microchip Technology

3.4.2.1
The HFINTOSC is factory calibrated but can be
adjusted in software by writing to the OSCTUNE
register (Register 3-1).
The OSCTUNE register has a tuning range of
approximately ±12%. The default value of the
OSCTUNE register is ‘0’. The value is a 5-bit two’s
complement number. Due to process variation, the
monotonicity and frequency step cannot be specified.
REGISTER 3-1:
© 2005 Microchip Technology Inc.
bit 7-5
bit 4-0
OSCTUNE Register
OSCTUNE – OSCILLATOR TUNING REGISTER (ADDRESS: 90h)
Unimplemented: Read as ‘0’
TUN<4:0>: Frequency Tuning bits
01111 = Maximum frequency
01110 =
•
•
•
00001 =
00000 = Oscillator module is running at the calibrated frequency.
11111 =
•
•
•
10000 = Minimum frequency
bit 7
Legend:
R = Readable bit
- n = Value at POR
U-0
—
U-0
—
PIC12F635/PIC16F636/639
U-0
Preliminary
—
W = Writable bit
‘1’ = Bit is set
R/W-0
TUN4
When the OSCTUNE register is modified, the
HFINTOSC frequency will begin shifting to the new
frequency. The HFINTOSC clock will stabilize within
1 ms. Code execution continues during this shift. There
is no indication that the shift has occurred.
OSCTUNE does not affect the LFINTOSC frequency.
Operation of features that depend on the LFINTOSC
clock source frequency, such as the Power-up Timer
(PWRT), Watchdog Timer (WDT), Fail-Safe Clock
Monitor (FSCM) and peripherals, are not affected by
the change in frequency.
R/W-0
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
TUN3
R/W-0
TUN2
x = Bit is unknown
R/W-0
TUN1
DS41232B-page 33
R/W-0
TUN0
bit 0