PIC17C752-08SLASHCL datasheet(189/328 Pages) MICROCHIP

189 / 328 page

DS30289A-page 189

PIC17C7XX

17.0

SPECIAL FEATURES OF THE

CPU

What sets a microcontroller apart from other proces-

sors are special circuits to deal with the needs of

real-time applications. The PIC17CXXX family has a

host of such features intended to maximize system reli-

ability, minimize cost through elimination of external

components, provide power saving operating modes

and offer code protection. These are:

• Oscillator selection (Section 4.0)

• Reset (Section 5.0)

- Power-on Reset (POR)

- Power-up Timer (PWRT)

- Oscillator Start-up Timer (OST)

- Brown-out Reset (BOR)

• Interrupts (Section 6.0)

• Watchdog Timer (WDT)

• SLEEP mode

• Code protection

The PIC17CXXX has a Watchdog Timer which can be

shutoff only through EPROM bits. It runs off its own RC

oscillator for added reliability. There are two timers that

offer necessary delays on POR and BOR. 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 96 ms (nominal) on power-up only,

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.

The SLEEP mode is designed to offer a very low cur-

rent power-down mode. The user can wake from

SLEEP through external reset, Watchdog Timer Reset

or through an interrupt. Several oscillator options are

also made available to allow the part to ﬁt the applica-

tion. The RC oscillator option saves system cost while

the LF crystal option saves power. Conﬁguration bits

are used to select various options. This conﬁguration

word has the format shown in Figure 17-1.

FIGURE 17-1: CONFIGURATION WORDS

U - x

R/P - 1

U - x

High (H) Table Read Addr.

—

PM2

BODEN

—

FE0Fh - FE08h

bit15

bit 8 bit 7

bit 0

U - x

R/P - 1

U - x R/P - 1

R/P - 1

Low (L) Table Read Addr.

—

PM1

—

PM0

WDTPS1 WDTPS0

FOSC1

FOSC0 FE07h - FE00h

bit15

bit 8 bit 7

bit 0

bit 6H

BODEN: Brown-out Detect Enable

1 =

Brown-out Detect circuitry is enabled

0 =

Brown-out Detect circuitry is disabled

bits 7H:6L:4L PM2, PM1, PM0, Processor Mode Select bits

111 =

Microprocessor Mode

110 =

Microcontroller mode

101 =

Extended microcontroller mode

000 =

Code protected microcontroller mode

bits 2L:3L

WDTPS1:WDTPS0, WDT Postscaler Select bits

11 =

WDT enabled, postscaler = 1

10 =

WDT enabled, postscaler = 256

01 =

WDT enabled, postscaler = 64

00 =

WDT disabled, 16-bit overﬂow timer

bits 1L:0L

FOSC1:FOSC0, Oscillator Select bits

11 =

EC oscillator

10 =

XT oscillator

01 =

RC oscillator

00 =

LF oscillator

—

Reserved

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