CF745 datasheet(31/217 Pages) MICROCHIP

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Preliminary

DS30453B-page 31

PIC16C5X

7.0

SPECIAL FEATURES OF THE

CPU

What

sets

microcontroller

apart

from

other

processors are special circuits that deal with the

needs of real-time applications. The PIC16C5X family

of microcontrollers 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 features are:

• Oscillator selection

• Reset

• Power-On Reset (POR)

• Device Reset Timer (DRT)

• Watchdog Timer (WDT)

(not implemented on PIC16C52)

• SLEEP

• Code protection

• ID locations (not implemented on PIC16C52)

The PIC16C5X Family has a Watchdog Timer which

can be shut off only through conﬁguration bit WDTE. It

runs off of its own RC oscillator for added reliability.

There is an 18 ms delay provided by the Device Reset

Timer (DRT), intended to keep the chip in reset until

the crystal oscillator is stable. With this timer 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 or through a Watchdog

Timer time-out. 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.

7.1

Conﬁguration Bits

Conﬁguration bits can be programmed to select

various device conﬁgurations. Two bits are for the

selection of the oscillator type and one bit is the

Watchdog Timer enable bit.

Nine bits are code

protection bits (Figure 7-1 and Figure 7-2) for the

PIC16C54,

PIC16CR54,

PIC16C56,

PIC16CR56,

PIC16C58, and PIC16CR58 devices.

QTP or ROM devices have the oscillator conﬁguration

programmed at the factory and these parts are tested

accordingly

(see

"Product

Identiﬁcation

System"

diagrams in the back of this data sheet).

FIGURE 7-1:

CONFIGURATION WORD FOR

PIC16CR54A/C54B/CR54B/C54C/CR54C/C55A/C56A/CR56A/C57C/

CR57B/CR57C/C58B/CR58A/CR58B

WDTE FOSC1 FOSC0

CONFIG

Address(1):

FFFh

bit11

987654321

bit0

bit 11-3: CP: Code protection bits

1 = Code protection off

0 = Code protection on

bit 2:

WDTE: Watchdog timer enable bit

1 = WDT enabled

0 = WDT disabled

bit 1-0:

FOSC1:FOSC0: Oscillator selection bits

11 = RC oscillator

10 = HS oscillator

01 = XT oscillator

00 = LP oscillator

Note 1:

Refer to the PIC16C5X Programming Speciﬁcation (Literature Number DS30190) to deter-

mine how to access the conﬁguration word.

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