Datasheet

Chapter 22
Watchdog (WDOG)
22.1 Introduction
The watchdog timer (WDOG) module is an independent timer that is available for system
use. It provides a safety feature to ensure that software is executing as planned and that
the CPU is not stuck in an infinite loop or executing unintended code. If the WDOG
module is not serviced (refreshed) within a certain period, it resets the MCU.
22.1.1 Features
Features of the WDOG module include:
• Configurable clock source inputs independent from the bus clock
• Internal 32 kHz RC oscillator
• Internal 1 kHz RC oscillator
• External clock source
• Programmable timeout period
• Programmable 16-bit timeout value
• Optional fixed 256 clock prescaler when longer timeout periods are needed
• Robust write sequence for counter refresh
• Refresh sequence of writing 0xA602 and then 0xB480 within 16 bus clocks
• Window mode option for the refresh mechanism
• Programmable 16-bit window value
MC9S08PA60 Reference Manual, Rev. 1, 9/2012
Freescale Semiconductor, Inc. 575