16F84A Microchip Technology, 16F84A Datasheet - Page 21

• Manufacturer Part Number: 16F84A
• Description: 18-pin Enhanced Flash/EEPROM 8-Bit Microcontroller
• Manufacturer: Microchip Technology

6.0
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
components, provide power saving operating modes
and offer code protection. These features are:
• OSC Selection
• Reset
• Interrupts
• Watchdog Timer (WDT)
• SLEEP
• Code protection
• ID locations
• In-circuit serial programming
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
FIGURE 6-1:
1998 Microchip Technology Inc.
- Power-on Reset (POR)
- Power-up Timer (PWRT)
- Oscillator Start-up Timer (OST)
bit13
bit 13:4 CP: Code Protection bit
bit 3
bit 2
bit 1:0
R/P-u R/P-u R/P-u R/P-u R/P-u R/P-u R/P-u R/P-u R/P-u R/P-u
CP
SPECIAL FEATURES OF THE
CPU
CP
cost
1 = Code protection off
0 = All 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
through
CONFIGURATION WORD - PIC16F84A
CP
CP
elimination
CP
CP
of
CP
external
Preliminary
CP
CP
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 (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
(DS33023).
6.1
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.
CP
PICmicro™
Configuration Bits
PWRTE WDTE FOSC1 FOSC0
R/P-u
R/P-u
Mid-Range
R = Readable bit
P = Programmable bit
- n = Value at POR reset
PIC16F84A
R/P-u
u = unchanged
Reference
R/P-u
DS35007A-page 21
bit0
Manual,