PIC16C63A/65B/73B/74B
13.0
SPECIAL FEATURES OF THE
CPU
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 (nominal) on power-up only and 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, WDT 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.
What sets a microcontroller apart from other proces-
sors are special circuits to deal with the needs of real-
time applications. The PIC16CXX family has a host of
such features intended to maximize system reliability,
minimize cost through elimination of external compo-
nents, provide power saving operating modes and offer
code protection. 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 (ICSP)
The PIC16CXX 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
13.1
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, and can be accessed
only during programming.
REGISTER 13-1:
CP1
bit 13
CONFIGURATION WORD (CONFIG 2007h)
CP1
CP0
CP1
CP0
—
BODEN
CP1
CP0
PWRTE WDTE FOSC1 FOSC0
bit 0
CP0
bits 13-8,
CP1:CP0:
Code Protection bits
(2)
5-4
11
= Code protection off
10
= Upper half of program memory code protected
01
= Upper 3/4th of program memory code protected
00
= All memory is code protected
bit 7
bit 6
Unimplemented:
Read as '1'
BODEN:
Brown-out Reset Enable bit
(1)
1
= BOR enabled
0
= BOR disabled
PWRTE:
Power-up Timer Enable bit
(1)
1
= PWRT disabled
0
= PWRT 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
Note 1:
Enabling Brown-out Reset automatically enables Power-up Timer (PWRT), regardless of the value of
PWRTE.
2:
All of the CP1:CP0 pairs have to be given the same value to enable the code protection scheme listed.
bit 3
bit 2
bit 1-0
2000 Microchip Technology Inc.
DS30605C-page 85
MICROCHIP [ MICROCHIP TECHNOLOGY ]
