mcf5282 Freescale Semiconductor, Inc, mcf5282 Datasheet - Page 355

• Manufacturer Part Number: mcf5282
• Manufacturer: Freescale Semiconductor, Inc

Chapter 18
Watchdog Timer Module
18.1
The watchdog timer is a 16-bit timer used to help software recover from runaway code. The watchdog
timer has a free-running down-counter (watchdog counter) that generates a reset on underflow. To prevent
a reset, software must periodically restart the countdown by servicing the watchdog.
18.2
This subsection describes the operation of the watchdog module in low-power modes and halted mode of
operation. Low-power modes are described in
watchdog module operation in the low-power modes, and shows how this module may facilitate exit from
each mode.
In wait mode with the watchdog control register’s WAIT bit (WCR[WAIT]) set, watchdog timer operation
stops. In wait mode with the WCR[WAIT] bit cleared, the watchdog timer continues to operate normally.
In doze mode with the WCR[DOZE] bit set, the watchdog timer module operation stops. In doze mode
with the WCR[DOZE] bit cleared, the watchdog timer continues to operate normally. Watchdog timer
operation stops in stop mode. When stop mode is exited, the watchdog timer continues to operate in its
pre-stop mode state.
In halted mode with the WCR[HALTED] bit set, watchdog timer module operation stops. In halted mode
with the WCR[HALTED] bit cleared, the watchdog timer continues to operate normally. When halted
mode is exited, watchdog timer operation continues from the state it was in before entering halted mode,
but any updates made in halted mode remain.
Freescale Semiconductor
Low-power Mode
Introduction
Low-Power Mode Operation
Halted
Doze
Wait
Stop
Table 18-1. Watchdog Module Operation in Low-power Modes
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3
Normal if WCR[HALTED] cleared,
Normal if WCR[DOZE] cleared,
Normal if WCR[WAIT] cleared,
Watchdog Operation
stopped otherwise
stopped otherwise
stopped otherwise
Stopped
Chapter 7, “Power
Upon Watchdog reset
Upon Watchdog reset
No
Upon Watchdog reset
Management.” Table 3-1 shows the
Mode Exit
18-1