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Infineon Technologies TC1796 User Manual

Infineon Technologies TC1796
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TC1796
System Units (Vol. 1 of 2)
Watchdog Timer
User’s Manual 16-16 V2.0, 2007-07
WDT, V2.0
16.4.6.4 Prewarning Mode Details
Prewarning Mode is always entered immediately after a Watchdog error condition was
detected. This can be either an access error to register WDT_CON0 or an overflow of
the counter in Normal or Time-Out Mode. This mode indicates that a reset of the device
is imminent. Operation of the WDT in this mode can not be altered or stopped, except
through a reset.
Note: In Prewarning Mode, the device does not have to wait for the end of the Time-out
Period and the reset. After having saved required state in the NMI routine,
Table 16-7 WDT Prewarning Mode
State /
Action
Description
Entry Detection of a Watchdog error:
Overflow of timer WDTTIM.
Access error to register WDT_CON0 (either on a password or Modify
Access) in Time-Out, Normal, or Disable modes.
Actions on
Entry
NMIWDT in register NMISR is set (this triggers an NMI request to the
CPU).
WDTTIM is set to FFFC
H
.
WDTPR is set to 1; WDTDS is set to 0; WDTIS retains its value.
WDTTO retains its previous value: If entry into Prewarning Mode was
from Time-Out Mode, WDTTO is 1. In all other cases, WDTTO is 0.
Bits WDTAE and WDTOE indicate whether Prewarning Mode was
entered due to an access or an overflow error. They have been set
accordingly on exit of the previous mode.
Operation Timer WDT_TIM starts counting up from FFFC
H
with frequency
selected through WDTIS.
Register WDT_CON0 can be accessed in this mode as usual.
However, the WDT will not change its mode anymore, regardless
whether valid or invalid accesses are made to WDT_CON0. For invalid
accesses to WDT_CON0 (Password or Modify Access), however, bit
WDTAE in WDT_SR will be set.
Register WDT_CON1 can not be written to in Prewarning Mode, even
if bit ENDINIT = 0. Write access to WDT_CON1 is totally prohibited.
Exit Prewarning Mode can not be disabled, prolonged, or terminated
(except through a reset). The timer will increment until it overflows from
FFFF
H
to 0000
H
, which then causes a system reset. Bit WDTRST in
register RSTSR is set in this case.
Next Mode Reset

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Infineon Technologies TC1796 Specifications

General IconGeneral
BrandInfineon Technologies
ModelTC1796
CategoryController
LanguageEnglish