saa-xc866 Infineon Technologies Corporation, saa-xc866 Datasheet - Page 67

• Manufacturer Part Number: saa-xc866
• 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 SAA-XC866 system reset. Hence, routine service of the WDT
confirms that the system is functioning properly. This ensures that an accidental
malfunction of the SAA-XC866 will be aborted in a user-specified time period. In debug
mode, the WDT is suspended and stops counting. Therefore, there is no need to refresh
the WDT during debugging.
Features:
• 16-bit Watchdog Timer
• Programmable reload value for upper 8 bits of timer
• Programmable window boundary
• Selectable input frequency of f
• Time-out detection with NMI generation and reset prewarning activation (after which
The WDT is a 16-bit timer incremented by a count rate of f
16-bit 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 27
Data Sheet
ENWDT
ENWDT_P
a system reset will be performed)
Figure 27
f
PCLK
Watchdog Timer
Logic
WDT Block Diagram
shows the block diagram of the WDT unit.
1:128
1:2
PCLK
/2 or f
WDTIN
MUX
63
PCLK
/128
WDT Low Byte
Control
WDT
Overflow/Time-out Control &
Window-boundary control
Clear
PCLK
Functional Description
WDT High Byte
WDTWINB
/2 or f
WDTREL
PCLK
SAA-XC866
V1.2, 2008-02
/128. This
WDTTO
WDTRST