User’s Manual
C166S V1 SubSystem
Watchdog Timer
User’s Manual
9-1
V 1.6, 2001-08
9
Watchdog Timer
To allow recovery from software or hardware failure, the User’s Manual provides a
Watchdog Timer
1)
. If the software fails to service this timer before an overflow occurs,
a watchdog timer reset can be initiated and a watchdog timer overflow can be signaled
by wdtint_n_o.
When the watchdog timer reset is enabled (default) and the software has been designed
to service it regularly before it overflows, the watchdog timer will supervise the program
execution as it only will overflow if the program does not progress properly. The
watchdog timer will also time out if a software error was due to hardware related failures.
This prevents the controller from malfunctioning for longer than a user-specified time.
The watchdog timer reset resets the CPU, Interruptcontroller, the External Bus
Controller, the Control Block and the WDT itself.
The wdtint_n_o always shows the occurrence of a watchdog timer overflow. If the
watchdog timer reset is disabled, the WDTINT signal can be used to trigger an interrupt.
The wdtint_n_o signals can be directly connected to one interrupt control node. The
watchdog timer can be used as a running timer and generates a periodical interrupt
request with the occurrence of a timer overflow. In case of an overflow the WDT counter
is automatically reloaded. Nevertheless the automatic reload is overruled in case of a
WDT reset (wdt reset not disabled). The WDT can still be serviced with the execution of
the srvwdt instruction.
Note: The WDT is automatically reloaded in case of a WDT overflow. In case of an
enabled WDT reset, the generated reset resets the WDT and overrules the reload
mechanism.
The watchdog timer provides two 16-bit registers and two subsystem signals:
• a read-only timer register that contains the current count,
• a control register for initialization and reset source detection,
• a conf_wdt_en_i subsystem signal to disable globally the WDT and
• a wdtint_o subsystem signal to signal a watchdog timer overflow.
The 16-bit watchdog timer is realized as two concatenated 8-bit timers. The upper 8 bits
of the watchdog timer can be preset to a user-programmable value via a watchdog
service access in order to vary the watchdog expire time. The lower 8 bits are reset upon
each service access.
The watchdog timer is a 16-bit up counter which is clocked with the prescaled PDBus+
clock (
f
PD
). The prescaler divides the PDBus+ clock
• by 2 (WDTIN = ’0’, WDTPRE = ’0’), or
• by 4 (WDTIN = ’0’, WDTPRE = ’1’), or
1)
The WDT can be globally disabled by the conf_wdt_en subsystem signal.
Содержание C166S V1 SubSystem
Страница 10: ...User s Manual C166S V1 SubSystem User s Manual I 6 V 1 6 2001 08...
Страница 16: ...User s Manual C166S V1 SubSystem Introduction User s Manual 1 6 V 1 6 2001 08...
Страница 126: ...User s Manual C166S V1 SubSystem Central Processing Unit User s Manual 3 96 V 1 6 2001 08...
Страница 178: ...User s Manual C166S V1 SubSystem Memory Organization User s Manual 4 52 V 1 6 2001 08...
Страница 206: ...User s Manual C166S V1 SubSystem Instruction Set User s Manual 5 28 V 1 6 2001 08...
Страница 306: ...User s Manual C166S V1 SubSystem Detailed Instruction Set User s Manual 6 100 V 1 6 2001 08...
Страница 362: ...User s Manual C166S V1 SubSystem The External Bus Interface User s Manual 8 40 V 1 6 2001 08...
Страница 452: ...User s Manual C166S V1 SubSystem General Purpose Timer Unit User s Manual 12 44 V 1 6 2001 08...
Страница 454: ...User s Manual C166S V1 SubSystem Instruction Index User s Manual 13 2 V 1 6 2001 08...
Страница 459: ......