PIC876 datasheet(121/218 Pages) MICROCHIP

121 / 218 page

 2001 Microchip Technology Inc.

DS30292C-page 119

PIC16F87X

12.0

SPECIAL FEATURES OF THE

CPU

All PIC16F87X devices have 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

PIC16F87X 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 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).

12.1

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.

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