XC2200 Derivatives
System Units (Vol. 1 of 2)
System Control Unit (SCU)
User’s Manual
6-210
V2.1, 2008-08
SCU, V1.13
6.11
Watchdog Timer (WDT)
The following part describes the Watchdog Timer (WDT) and its functionality.
6.11.1
Introduction
The Watchdog Timer (WDT) is a secure mechanism to overcome life- and dead-locks.
An enabled WDT generates a reset for the system if not serviced in a configured time
frame.
Features
The following list is a summary of the WDT functions:
•
16-bit Watchdog Timer
•
Selectable operating frequency:
f
IN
/ 256 or
f
IN
/ 16384
•
Timer overflow error detection
•
Individual disable for timer functionality
•
Double Reset Detection
provides an overview on the registers of the Watchdog Timer.
Figure 6-31 Watchdog Timer Register Overview
6.11.2
Overview
The Watchdog Timer (WDT) provides a highly reliable and secure way to detect and
recover from software or hardware failure. The WDT helps to abort an accidental
malfunction of the XC2200 in a user-specified time period. When enabled, the WDT will
cause the XC2200 system to be reset if the WDT is not serviced within a user-
programmable time period. The CPU must service the WDT within this time interval to
prevent the WDT from causing a WDT reset request trigger. Hence, regular service of
the WDT confirms that the system is functioning properly.
A further feature of the Watchdog Timer is its reset prewarning operation. Instead of
immediately resetting the device on the detection of an error, a prewarning output is
given to the system via an interrupt request. This makes it possible to bring the system
into a defined and predictable status, before the reset is finally issued.
WDT_Reg_Overview.vsd
WDTCS
W DT Control &
Status Register
WDTCS
WDTREL
WDTTIM
WDT Control and Status Register
WDT Reload Register
WDT Timer Register
WDTTIM
W DT Timer
Register
WDTREL
W DT Reload
Register