PIC16C717 Datasheet, PDF (125/200 Pages) Microchip Technology – 18/20-Pin, 8-Bit CMOS Microcontrollers with 10/12-Bit A/D

12.0 SPECIAL FEATURES OF THE
CPU
These devices have a host of features intended to
maximize system reliability, minimize cost through elim-
ination of external components, 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)
• Low-voltage detection
• SLEEP
• Code protection
• ID locations
• In-circuit serial programming (ICSP)
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 provides a
fixed delay of 72 ms (nominal) on power-up type resets
only (POR, BOR), designed to keep the part in reset
while the power supply stabilizes. With these two timers
on-chip, most applications need no external reset cir-
cuitry.
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 INTRC and ER oscillator options save system cost
while the LP crystal option saves power. A set of con-
figuration bits are 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. 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 -
3FFFh), which can be accessed only during program-
ming.
PIC16C717/770/771
Some of the core features provided may not be neces-
sary to each application that a device may be used for.
The configuration word bits allow these features to be
configured/enabled/disabled as necessary. These fea-
tures include code protection, brown-out reset and its
trippoint, the power-up timer, the watchdog timer and
the devices oscillator mode. As can be seen in
Figure 12-1, some additional configuration word bits
have been provided for brown-out reset trippoint selec-
tion.
© 1999 Microchip Technology Inc.
Advanced Information
DS41120A-page 125