12.0 SPECIAL FEATURES OF THE
CPU
What sets a microcontroller apart from other proces-
sors are special circuits to deal with the needs of real
time applications. The PIC16CXXX family has a host of
such features, intended to maximize system reliability,
minimize cost through elimination of external compo-
nents, provide power saving operating modes and offer
code protection. These are:
• Oscillator Selection
• RESET
- Power-on Reset (POR)
- Power-up Timer (PWRT)
- Oscillator Start-up Timer (OST)
- Brown-out Reset (BOR)
• Interrupts
• Watchdog Timer (WDT)
• SLEEP
• Code Protection
• ID Locations
• In-Circuit Serial Programming
The PIC16CXXX has a Watchdog Timer which can be
shut-off only through configuration bits. It runs off its
own RC oscillator for added reliability.
There are 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 72 ms (nomi-
nal) on power-up only, designed to keep the part in
PIC16C925/926
RESET while the power supply stabilizes. With these
two timers on-chip, most applications need no external
RESET circuitry.
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, or
through an interrupt.
Several oscillator options are also made available to
allow the part to fit the application. The RC oscillator
option saves system cost, while the LP crystal option
saves power. A set of configuration bits are used to
select various options.
12.1 Configuration Bits
The configuration bits can be programmed (read as '0'),
or left unprogrammed (read as '1'), to select various
device configurations. These bits are mapped in pro-
gram memory location 2007h.
The user will note that address 2007h is beyond the user
program memory space and can be accessed only dur-
ing programming.
2001 Microchip Technology Inc.
Preliminary
DS39544A-page 97