PIC16F-ESLASHML datasheet(97/178 Pages) MICROCHIP

97 / 178 page

DS40044F-page 95

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:

OSC selection

Reset

Power-on Reset (POR)

Power-up Timer (PWRT)

Oscillator Start-Up Timer (OST)

Brown-out Reset (BOR)

Interrupts

Watchdog Timer (WDT)

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.

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