
Freescale Semiconductor
27-1
Chapter 27
Watchdog Timer Module
27.1
Introduction
The watchdog timer (WDT) 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.
27.1.1
Low-Power Mode Operation
This subsection describes the operation of the watchdog module in low-power modes and halted mode of
operation (by issuing a HALT instruction). Low-power modes are described in
shows the 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 (entered by issuing a HALT instruction or asserting BKPT) with the WCR[HALTED] bit
set, watchdog timer module operation stops. 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. If the WCR[HALTED] bit is cleared, the watchdog timer continues to operate normally after
executing a HALT instruction. This is a debug feature available for the user
Table 27-1. Watchdog Module Operation in Low-power Modes
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, only via external interrupts
MCF5329 Reference Manual, Rev 3
Summary of Contents for MCF5329
Page 106: ...ColdFire Core 3 32 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 148: ...Cache 5 22 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 154: ...Static RAM SRAM 6 6 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 184: ...Power Management 8 18 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 204: ...Reset Controller Module 10 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 220: ...System Control Module SCM 11 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 228: ...Crossbar Switch XBS 12 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 268: ...General Purpose I O Module 13 40 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 392: ...SDRAM Controller SDRAMC 18 30 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 436: ...Fast Ethernet Controller FEC 19 44 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 594: ...FlexCAN 23 30 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 678: ...Pulse Width Modulation PWM Module 26 22 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 684: ...Watchdog Timer Module 27 6 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 704: ...DMA Timers DTIM0 DTIM3 29 12 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 754: ...UART Modules 31 34 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 770: ...I2 C Interface 32 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 866: ...Debug Module 36 50 Freescale Semiconductor MCF5329 Reference Manual Rev 3...