PIC16F84A_07 Datasheet, PDF (23/88 Pages) Microchip Technology – 18-pin Enhanced FLASH/EEPROM 8-bit Microcontroller

PIC16F84A
6.0 SPECIAL FEATURES OF THE
CPU
What sets a microcontroller apart from other
processors are special circuits to deal with the needs of
real time applications. The PIC16F84A has a host of
such features intended to maximize system reliability,
minimize cost through elimination of external
components, provide power saving operating modes
and offer code protection. These features are:
• OSC Selection
• RESET
- Power-on Reset (POR)
- Power-up Timer (PWRT)
- Oscillator Start-up Timer (OST)
• Interrupts
• Watchdog Timer (WDT)
• SLEEP
• Code Protection
• ID Locations
• In-Circuit Serial Programming™ (ICSP™)
The PIC16F84A 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 pro-
vides a fixed delay of 72 ms (nominal) on power-up
only. This design keeps the device in RESET while the
power supply stabilizes. With these two timers on-chip,
most applications need no external RESET circuitry.
SLEEP mode offers a very low current power-down
mode. The user can wake-up from SLEEP through
external RESET, Watchdog Timer Time-out or through
an interrupt. Several oscillator options are provided 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 the various options.
Additional information on special features is available
in the PICmicro™ Mid-Range Reference Manual
(DS33023).
6.1 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
program memory location 2007h.
Address 2007h is beyond the user program memory
space and it belongs to the special test/configuration
memory space (2000h - 3FFFh). This space can only
be accessed during programming.
REGISTER 6-1: PIC16F84A CONFIGURATION WORD
R/P-u
CP
bit13
R/P-u R/P-u
CP CP
R/P-u
CP
R/P-u R/P-u R/P-u R/P-u R/P-u
CP CP CP CP CP
R/P-u R/P-u R/P-u
CP PWRTE WDTE
R/P-u
F0SC1
R/P-u
F0SC0
bit0
bit 13-4
bit 3
bit 2
bit 1-0
CP: Code Protection bit
1 = Code protection disabled
0 = All program memory is code protected
PWRTE: Power-up Timer Enable bit
1 = Power-up Timer is disabled
0 = Power-up Timer is enabled
WDTE: Watchdog Timer Enable bit
1 = WDT enabled
0 = WDT disabled
FOSC1:FOSC0: Oscillator Selection bits
11 = RC oscillator
10 = HS oscillator
01 = XT oscillator
00 = LP oscillator
© 2001 Microchip Technology Inc.
DS35007B-page 21