PIC18F44J10-ISLASHSOSQTP datasheet(244/368 Pages) MICROCHIP

244 / 368 page

PIC18F45J10 FAMILY

DS39682E-page 242

21.2

Watchdog Timer (WDT)

For PIC18F45J10 family devices, the WDT is driven by

the INTRC oscillator. When the WDT is enabled, the

clock source is also enabled. The nominal WDT period

is 4 ms and has the same stability as the INTRC

oscillator.

The 4 ms period of the WDT is multiplied by a 16-bit

postscaler. Any output of the WDT postscaler is selected

by a multiplexor, controlled by the WDTPS bits in Config-

uration Register 2H. Available periods range from about

4 ms to 135 seconds (2.25 minutes) depending on volt-

age, temperature and Watchdog postscaler. The WDT

and postscaler are cleared whenever a SLEEP or

CLRWDT

instruction is executed, or a clock failure

(primary or Timer1 oscillator) has occurred.

21.2.1

CONTROL REGISTER

The WDTCON register (Register 21-9) is a readable

and writable register. The SWDTEN bit enables or

disables WDT operation.

FIGURE 21-1:

WDT BLOCK DIAGRAM

TABLE 21-2:

SUMMARY OF WATCHDOG TIMER REGISTERS

Note 1:

The CLRWDT and SLEEP instructions

clear the WDT and postscaler counts

when executed.

When a CLRWDT instruction is executed,

the postscaler count will be cleared.

WDTCON: WATCHDOG TIMER CONTROL REGISTER

u-0

U-0

R/W-0

—

—SWDTEN(1)

bit 7

bit 0

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

bit 7-1

Unimplemented

: Read as ‘0’

bit 0

SWDTEN:

Software Controlled Watchdog Timer Enable bit(1)

= Watchdog Timer is on

= Watchdog Timer is off

Note 1:

This bit has no effect if the Configuration bit, WDTEN, is enabled.

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Reset Values

on page

RCON

IPEN

—

POR

BOR

WDTCON

—

—SWDTEN

Legend:

— = unimplemented, read as ‘0’. Shaded cells are not used by the Watchdog Timer.

INTRC Oscillator

WDT

Wake-up from

Reset

WDT

WDT Counter

Programmable Postscaler

1:1 to 1:32,768

Enable WDT

WDTPS<3:0>

SWDTEN

CLRWDT

Power-Managed

Reset

All Device Resets

Sleep

INTRC Control

÷128

Modes

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