saf-xc888cm-8ffi5v Infineon Technologies Corporation, saf-xc888cm-8ffi5v Datasheet - Page 87

• Manufacturer Part Number: saf-xc888cm-8ffi5v
• Description: 8-bit Single-chip Microcontroller
• Manufacturer: Infineon Technologies Corporation

3.10
The Watchdog Timer (WDT) provides a highly reliable and secure way to detect and
recover from software or hardware failures. The WDT is reset at a regular interval that is
predefined by the user. The CPU must service the WDT within this interval to prevent the
WDT from causing an XC886/888 system reset. Hence, routine service of the WDT
confirms that the system is functioning properly. This ensures that an accidental
malfunction of the XC886/888 will be aborted in a user-specified time period.
In debug mode, the WDT is default suspended and stops counting. Therefore, there is
no need to refresh the WDT during debugging.
Features
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The WDT is a 16-bit timer incremented by a count rate of
timer is realized as two concatenated 8-bit timers. The upper 8 bits of the WDT can be
preset to a user-programmable value via a watchdog service access in order to modify
the watchdog expire time period. The lower 8 bits are reset on each service access.
Figure 28
Figure 28
Data Sheet
ENWDT
ENWDT_P
16-bit Watchdog Timer
Programmable reload value for upper 8 bits of timer
Programmable window boundary
Selectable input frequency of
Time-out detection with NMI generation and reset prewarning activation (after which
a system reset will be performed)
f
PCLK
shows the block diagram of the WDT unit.
Watchdog Timer
Logic
WDT Block Diagram
1:128
1:2
f
PCLK
WDTIN
/2 or
MUX
80
f
PCLK
/128
WDT Low Byte
Control
WDT
Overflow/Time-out Control &
Window-boundary control
Clear
f
PCLK
/2 or
Functional Description
WDT High Byte
WDTWINB
WDTREL
f
PCLK
XC886/888CLM
/128. This 16-bit
V1.1, 2009-01
FNMIWDT
WDTRST
.