Z8F082A28100KIT ZILOG [Zilog, Inc.], Z8F082A28100KIT Datasheet - Page 97

• Manufacturer Part Number: Z8F082A28100KIT
• Description: Z8 Encore XP-R F08xA Series with eXtended Peripherals
• Manufacturer: ZILOG [Zilog, Inc.]

Watch-Dog Timer
Overview
Operation
PS024705-0405
The Watch-Dog Timer (WDT) protects against corrupt or unreliable software, power
faults, and other system-level problems which may place the Z8 Encore! XP
Series devices into unsuitable operating states. The Watch-Dog Timer includes the follow-
ing features:
•
•
•
The Watch-Dog Timer (WDT) is a retriggerable one-shot timer that resets or interrupts the
Z8 Encore! XP
Watch-Dog Timer uses a dedicated on-chip RC oscillator as its clock source. The Watch-
Dog Timer operates in only two modes: ON and OFF. Once enabled, it always counts and
must be refreshed to prevent a time-out. Perform an enable by executing the WDT instruc-
tion or by setting the WDT_AO Flash Option Bit. The WDT_AO bit forces the Watch-
Dog Timer to operate immediately upon reset, even if a WDT instruction has not been
executed.
The Watch-Dog Timer is a 24-bit reloadable downcounter that uses three 8-bit registers in
the eZ8 CPU register space to set the reload value. The nominal WDT time-out period is
described by the following equation:
where the WDT reload value is the decimal value of the 24-bit value given by
{WDTU[7:0], WDTH[7:0], WDTL[7:0]} and the typical Watch-Dog Timer RC oscillator
frequency is 10KHz. The Watch-Dog Timer cannot be refreshed after it reaches
The WDT Reload Value must not be set to values below
information about approximate time-out delays for the minimum and maximum WDT
reload values.
WDT Time-out Period (ms)
On-chip RC oscillator
A selectable time-out response: reset or interrupt
24-bit programmable time-out value
®
F08xA Series devices when the WDT reaches its terminal count. The
P R E L I M I N A R Y
=
WDT Reload Value
------------------------------------------------- -
10
Z8 Encore! XP
000004H
Product Specification
. Table 55 provides
®
Watch-Dog Timer
F08xA Series
®
F08xA
000002H
.
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