PIC16F627A_05 Datasheet, PDF (97/180 Pages) Microchip Technology – Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology

PIC16F627A/628A/648A
14.0 SPECIAL FEATURES OF THE
CPU
Special circuits to deal with the needs of real-time
applications are what sets a microcontroller apart from
other processors. The PIC16F627A/628A/648A family
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 are:
1. OSC selection
2. Reset
3. Power-on Reset (POR)
4. Power-up Timer (PWRT)
5. Oscillator Start-Up Timer (OST)
6. Brown-out Reset (BOR)
7. Interrupts
8. Watchdog Timer (WDT)
9. Sleep
10. Code protection
11. ID Locations
12. In-Circuit Serial Programming™ (ICSP™)
The PIC16F627A/628A/648A has a Watchdog Timer
which is controlled by 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
only, designed to keep the part in Reset while the
power supply stabilizes. There is also circuitry to reset
the device if a brown-out occurs. With these three
functions on-chip, most applications need no external
Reset circuitry.
The 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 are used to select various options.
14.1 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.
The user will note that address 2007h is beyond the
user program memory space. In fact, it belongs to the
special configuration memory space (2000h-3FFFh),
which can be accessed only during programming. See
“PIC16F627A/628A/648A EEPROM Memory
Programming Specification” (DS41196) for additional
information.
© 2005 Microchip Technology Inc.
DS40044D-page 95