EZ80F91MCU Datasheet, PDF (141/396 Pages) Zilog, Inc. – eZ80Acclaim-TM Flash Microcontrollers

eZ80F91 MCU
Product Specification
122
Watch-Dog Timer
Watch-Dog Timer Overview
The Watch-Dog Timer (WDT) helps protect against corrupt or unreliable software,
power faults, and other system-level problems which can place the CPU into
unsuitable operating states. The eZ80F91 WDT features:
• Four programmable time-out periods: 2¹⁸, 2²², 2²⁵, and 2²⁷ clock cycles
• Three selectable WDT clock sources:
– Internal RC oscillator
– System clock
– Real-Time Clock source (on-chip 32Khz crystal oscillator or 50/60Hz
signal)
• A selectable time-out response: a time-out can be configured to generate
either a RESET or a nonmaskable interrupt (NMI)
• A WDT time-out RESET indicator flag
Figure 24 illustrates a block diagram of the Watch-Dog Timer.
Data[7:0]
WDT_CLK
RTC Clock
System Clock
28-Bit
Upcounter
WDT
Oscillator
Time-out Compare Logic
(WDT_PERIOD)
Figure 24. Watch-Dog Timer Block Diagram
PS019209-0504
PRELIMINARY
Control Register/
Reset Register
WDT Control Logic
RESET
NMI to eZ80^® CPU
Watch-Dog Timer