PIC16F631/677/685/687/689/690
14.0 SPECIAL FEATURES OF THE
CPU
The PIC16F631/677/685/687/689/690 have a host of
features intended to maximize system reliability,
minimize cost through elimination of external compo-
nents, provide power saving features and offer code
protection.
These features are:
• Reset
- Power-on Reset (POR)
- Power-up Timer (PWRT)
- Oscillator Start-up Timer (OST)
- Brown-out Reset (BOR)
• Interrupts
• Watchdog Timer (WDT)
• Oscillator selection
• Sleep
• Code protection
• ID Locations
• In-Circuit Serial Programming
The PIC16F631/677/685/687/689/690 have two timers
that offer necessary delays on power-up. One is the
Oscillator Start-up Timer (OST), intended to keep the
chip in Reset until the crystal oscillator is stable. The
other is the Power-up Timer (PWRT), which provides a
fixed delay of 64 ms (nominal) on power-up only,
designed to keep the part in Reset while the power
supply stabilizes. There is also circuitry to reset the
device if a brown-out occurs, which can use the Power-
up Timer to provide at least a 64 ms Reset. With these
three functions-on-chip, most applications need no
external Reset circuitry.
The Sleep mode is designed to offer a very low-current
Power-down mode. The user can wake-up from Sleep
through:
• External Reset
• Watchdog Timer Wake-up
• An interrupt
Several oscillator options are also made available to
allow the part to fit the application. The INTOSC option
saves system cost while the LP crystal option saves
power. A set of Configuration bits are used to select
various options (see Register 14-2).
© 2007 Microchip Technology Inc.
DS41262D-page 193
MICROCHIP [ MICROCHIP ]
