W78L801 Datasheet, PDF(8/20 Page) Winbond

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W78L801 Datasheet, PDF (8/20 Pages) Winbond – 8-BIT MICROCONTROLLER

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W78L801

Table.1 Priority level for simultaneous requests of the same priority interrupt sources

SOURCE

External Interrupt 0

External Interrupt 5

Timer 0 Overflow

External Interrupt 6

External Interrupt 1

External Interrupt 2

External Interrupt 7

Timer 1 Overflow

External Interrupt 3

External Interrupt 8

External Interrupt 4

External Interrupt 9

FLAG

IE0

IQ5

TF0

IQ6

IE1

IQ2

IQ7

TF1

IQ3

IQ8

IQ4

IQ9

PRIORITY LEVEL

(highest)

(lowest)

VECTOR ADDRESS

0003H

0053H

000BH

005BH

0013H

003BH

0063H

001BH

0043H

006BH

004BH

0073H

Watchdog Timer

The Watchdog timer is a free-running timer which can be programmed by the user to serve as a

system monitor, a time-base generator or an event timer. It is basically a set of dividers that divide

the system clock. The divider output is selectable and determines the time-out interval. When the

time-out occurs, a system reset can be caused if it is enabled. The main use of the Watchdog timer is

as a system monitor. This is important in real-time control applications. In case of power glitches or

electro-magnetic interference, the processor may begin to execute errant code. If this is left

unchecked the entire system may crash. The watchdog time-out selection will result in different time-

out values depending on the clock speed. The Watchdog timer will be disabled on reset. In general,

software should restart the Watchdog timer to put it into a known state. The control bits that support

the Watchdog timer are discussed below.

Watchdog Timer Control Register

Bit:

ENW CLRW WIDL -

PS2 PS1 PS0

Mnemonic: WDTC

Address: 8FH

ENW : Enable watch-dog if set.

CLRW : Clear watch-dog timer and prescaler if set. This flag will be cleared automatically

WIDL : If this bit is set, watch-dog is enabled under IDLE mode. If cleared, watch-dog is disabled

under IDLE mode. Default is cleared.

PS2, PS1, PS0 : Watch-dog prescaler timer select. Prescaler is selected when set PS2â0 as follows:

PS2 PS1 PS0

00 0

01 0

PRESCALER SELECT

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