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17. Watchdog Timer (WDT)
17.1
Description
The Watchdog Timer can be used to prevent system lock-up if the software becomes trapped in
a deadlock. It features a 12-bit down counter that allows a watchdog period of up to 16 seconds
(slow clock at 32.768 kHz). It can generate a general reset or a processor reset only. In addition,
it can be stopped while the processor is in debug mode or idle mode.
17.2
Embedded Features
• 16-bit Key-protected only-once Programmable Counter
• Provides Reset or Interrupt Signals to the System
• Windowed, prevents the processor to be in a dead lock on the watchdog access
• Counter May Be Stopped While the Processor is in Debug State or in Idle Mode
• AMBA
™
-compliant Interface
– Interfaces to the ARM
®
Advanced Peripheral Bus
17.3
Block Diagram
Figure 17-1.
Watchdog Timer Block Diagram
= 0
1
0
set
reset
read WDT_SR
or
reset
wdt_fault
(to Reset Controller)
set
reset
WDFIEN
wdt_int
WDT_MR
SLCK
1/128
12-bit Down
Counter
Current
Value
WDD
WDT_MR
<= WDD
WDV
WDRSTT
WDT_MR
WDT_CR
reload
WDUNF
WDERR
reload
write WDT_MR
WDT_MR
WDRSTEN
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