PIC16F872_06 Datasheet, PDF (89/168 Pages) Microchip Technology – 28-Pin, 8-Bit CMOS Flash Microcontroller with 10-Bit A/D

11.0 SPECIAL FEATURES OF THE
CPU
The PIC16F872 microcontroller has a host of features
intended to maximize system reliability, minimize cost
through elimination of external components, provide
power saving operating modes and offer code protec-
tion. 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
• Low Voltage In-Circuit Serial Programming
• In-Circuit Debugger
The microcontrollers have 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. It is designed to keep the part in
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 is used to
select various options.
Additional information on special features is available
in the PICmicro™ Mid-Range Reference Manual,
(DS33023).
PIC16F872
11.1 Configuration Bits
The configuration bits can be programmed (read as '0'),
or left unprogrammed (read as '1'), to select various
device configurations. The erased, or unprogrammed,
value of the configuration word is 3FFFh. These bits
are mapped in program memory location 2007h.
It is important to note that address 2007h is beyond the
user program memory space, which can be accessed
only during programming.
© 2006 Microchip Technology Inc.
DS30221C-page 87