EZ80L92MCU Datasheet, PDF (87/241 Pages) Zilog, Inc. – eZ80Acclaim Flash Microcontrollers

eZ80L92 MCU
Product Specification
72
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 may place the eZ80^® CPU into unsuitable
operating states. The eZ80L92 WDT features:
• Four programmable time-out periods: 2¹⁸, 2²², 2²⁵, and 2²⁷ clock cycles
• Two selectable WDT clock sources: the system clock or the Real-Time Clock source
(on-chip 32 Khz crystal oscillator or 50/60 Hz signal)
• A selectable time-out response: a time-out can be configured to generate either a RE-
SET or a nonmaskable interrupt (NMI)
• A WDT time-out RESET indicator flag
Figure 17 illustrates the block diagram for the Watch-Dog Timer.
Data[7:0]
WDT_CLK
RTC Clock
System Clock
28-Bit
Upcounter
Time-Out Compare Logic
{WDT_PERIOD}
Figure 17. Watch-Dog Timer Block Diagram
Control Register/
Reset Register
WDT Control Logic
RESET
NMI to eZ80 CPU
PS013012-1004
PRELIMINARY
Watch-Dog Timer