PIC16F872 Datasheet, PDF (95/160 Pages) Microchip Technology – 28-Pin, 8-Bit CMOS FLASH Microcontroller

11.0 SPECIAL FEATURES OF THE
CPU
These devices have a host of features intended to max-
imize system reliability, minimize cost through elimina-
tion of external components, provide power saving
operating modes and offer code protection. These are:
• OSC 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
These devices 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 pro-
vides a fixed delay of 72 ms (nominal) 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 are 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. These bits are mapped in pro-
gram memory location 2007h.
The user will note that address 2007h is beyond the
user program memory space. In fact, it belongs to the
special test/configuration memory space (2000h
through 3FFFh), which can be accessed only during
programming.
© 1999 Microchip Technology Inc.
Preliminary
DS30221A-page 95