PIC18F4685-ISLASHSP datasheet(345/484 Pages) MICROCHIP

345 / 484 page

Preliminary

DS39761B-page 343

PIC18F2682/2685/4682/4685

24.0

SPECIAL FEATURES OF THE

CPU

PIC18F2682/2685/4682/4685 devices include several

features intended to maximize reliability and minimize

cost through elimination of external components.

These are:

• Oscillator Selection

• Resets:

- Power-on Reset (POR)

- Power-up Timer (PWRT)

- Oscillator Start-up Timer (OST)

- Brown-out Reset (BOR)

• Interrupts

• Watchdog Timer (WDT)

• Fail-Safe Clock Monitor

• Two-Speed Start-up

• Code Protection

• ID Locations

• In-Circuit Serial Programming

The oscillator can be configured for the application

depending on frequency, power, accuracy and cost. All

of the options are discussed in detail in Section 2.0

“Oscillator Configurations”.

A complete discussion of device Resets and interrupts

is available in previous sections of this data sheet.

In addition to their Power-up and Oscillator Start-up

Timers provided for Resets, PIC18F2682/2685/4682/

4685 devices have a Watchdog Timer, which is either

permanently enabled via the Configuration bits or

software controlled (if configured as disabled).

The inclusion of an internal RC oscillator also provides

the additional benefits of a Fail-Safe Clock Monitor

(FSCM) and Two-Speed Start-up. FSCM provides for

background monitoring of the peripheral clock and

automatic switchover in the event of its failure. Two-

Speed Start-up enables code to be executed almost

immediately on start-up, while the primary clock source

completes its start-up delays.

All of these features are enabled and configured by

setting the appropriate Configuration register bits.

24.1

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 starting

at program memory location 300000h.

The user will note that address 300000h is beyond the

user program memory space. In fact, it belongs to the

configuration memory space (300000h-3FFFFFh), which

can only be accessed using table reads and table writes.

Programming the Configuration registers is done in a

manner similar to programming the Flash memory. The

WR bit in the EECON1 register starts a self-timed write

to the Configuration register. In normal operation mode,

a TBLWT instruction with the TBLPTR pointing to the

Configuration register sets up the address and the data

for the Configuration register write. Setting the WR bit

starts a long write to the Configuration register. The

Configuration registers are written a byte at a time. To

write or erase a configuration cell, a TBLWT instruction

can write a ‘1’ or a ‘0’ into the cell. For additional details

on Flash programming, refer to Section 6.5 “Writing

to Flash Program Memory”.

TABLE 24-1:

CONFIGURATION BITS AND DEVICE IDs

File Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Default/

Unprogrammed

Value

300001h

CONFIG1H

IESO

FCMEN

—

FOSC3

FOSC2

FOSC1

FOSC0

00-- 0111

300002h

CONFIG2L

—

BORV1

BORV0

BOREN1

BOREN0

PWRTEN

---1 1111

300003h

CONFIG2H

—

WDTPS3

WDTPS2

WDTPS1

WDTPS0

WDTEN

---1 1111

300005h

CONFIG3H

MCLRE

—

LPT1OSC PBADEN

—

1--- -01-

300006h

CONFIG4L

DEBUG

XINST

BBSIZ1

BBSIZ2

—LVP

—STVREN

1000 -1-1

300008h

CONFIG5L

—

—CP5(1)

CP4

CP3

CP2

CP1

CP0

--11 1111

300009h

CONFIG5H

CPD

CPB

—

11-- ----

30000Ah

CONFIG6L

—

—WRT5(1)

WRT4

WRT3

WRT2

WRT1

WRT0

--11 1111

30000Bh

CONFIG6H

WRTD

WRTB

WRTC

—

111- ----

30000Ch

CONFIG7L

—

EBTR5(1)

EBTR4

EBTR3

EBTR2

EBTR1

EBTR0

--11 1111

30000Dh

CONFIG7H

—EBTRB

—

-1-- ----

3FFFFEh

DEVID1

DEV2

DEV1

DEV0

REV4

REV3

REV2

REV1

REV0

xxxx xxxx(2)

3FFFFFh

DEVID2

DEV10

DEV9

DEV8

DEV7

DEV6

DEV5

DEV4

DEV3

xxxx xxxx

(2)

Legend: x = unknown, u = unchanged, - = unimplemented, q = value depends on condition. Shaded cells are unimplemented, read as ‘0’.

Note 1:

Unimplemented in PIC18F2682/4682 devices; maintain this bIt set.

2: See Register 24-12 and Register 24-13 for DEVID1 and DEVID2 values. DEVID registers are read-only and cannot be

programmed by the user.

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