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MOTOROLA
Chapter 18. Watchdog Timer Module
18-1
Chapter 18
Watchdog Timer Module
18.1 Introduction
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 Low-Power Mode Operation
This subsection describes the operation of the watchdog module in low-power modes and
halted mode of operation. Low-power modes are described in Chapter 7, “Power
Management.” Table 3-1 shows the watchdog module operation in the low-power modes,
and shows how this module may facilitate exit from each mode.
Table 18-1. Watchdog Module Operation in Low-power Modes
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.
Low-power Mode
Watchdog Operation
Mode Exit
Wait
Normal if WCR[WAIT] cleared,
stopped otherwise
Upon Watchdog reset
Doze
Normal if WCR[DOZE] cleared,
stopped otherwise
Upon Watchdog reset
Stop
Stopped
No
Halted
Normal if WCR[HALTED] cleared,
stopped otherwise
Upon Watchdog reset
Summary of Contents for ColdFire MCF5281
Page 124: ...3 20 MCF5282 User s Manual MOTOROLA EMAC Instruction Set Summary ...
Page 141: ...MOTOROLA Chapter 5 Static RAM SRAM 5 5 SRAM Programming Model ...
Page 142: ...5 6 MCF5282 User s Manual MOTOROLA SRAM Programming Model ...
Page 168: ...6 26 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 186: ...7 18 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 228: ...9 22 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 246: ...10 18 MCF5282 User s Manual MOTOROLA Low Power Wakeup Operation ...
Page 254: ...11 8 MCF5282 User s Manual MOTOROLA Memory Map and Registers ...
Page 264: ...12 10 MCF5282 User s Manual MOTOROLA Chip Select Registers ...
Page 280: ...13 16 MCF5282 User s Manual MOTOROLA Misaligned Operands ...
Page 314: ...14 34 MCF5282 User s Manual MOTOROLA MCF5282 External Signals ...
Page 339: ...MOTOROLA Chapter 15 Synchronous DRAM Controller Module 15 25 SDRAM Example ...
Page 340: ...15 26 MCF5282 User s Manual MOTOROLA SDRAM Example ...
Page 356: ...16 16 MCF5282 User s Manual MOTOROLA DMA Controller Module Functional Description ...
Page 408: ...17 52 MCF5282 User s Manual MOTOROLA Buffer Descriptors ...
Page 446: ...20 24 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 474: ...22 18 MCF5282 User s Manual MOTOROLA Programming Model ...
Page 510: ...23 36 MCF5282 User s Manual MOTOROLA Operation ...
Page 526: ...24 16 MCF5282 User s Manual MOTOROLA I2C Programming Examples ...
Page 672: ...28 12 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 718: ...29 46 MCF5282 User s Manual MOTOROLA Motorola Recommended BDM Pinout ...
Page 750: ...32 8 MCF5282 User s Manual MOTOROLA Ordering Information ...