TC1796
System Units (Vol. 1 of 2)
Watchdog Timer
User’s Manual 16-12 V2.0, 2007-07
WDT, V2.0
16.4.5 Term Definitions for WDT_CON0 Accesses
To simplify the descriptions in the following sections, a number of terms are defined to
indicate the type of access to register WDT_CON0:
Watchdog Access Sequence: Two accesses to register WDT_CON0 consisting of first
a Password Access followed by a Modify Access. The two accesses do not have to be
adjacent accesses, any number of accesses to other addresses can occur between
these accesses as long as the Time-out Period is not exceeded.
Password Access: The first access of a Watchdog Access Sequence to register
WDT_CON0 intended to open WDT_CON0 for modifications. This access needs to write
a defined password value to WDT_CON0 in order to successfully open WDT_CON0.
Valid Password Access: A Password Access with the correct password value. A Valid
Password Access opens register WDT_CON0 for one, and only one, Modify Access. Bit
WDTLCK is set to 0 after this access. The WDT is placed into the Time-Out Mode after
a Valid Password Access in Normal Mode or Disabled Mode.
Modify Access: The second access of an Watchdog Access Sequence to register
WDT_CON0 intended to modify parameters in WDT_CON0. The parameters that can
be modified are WDTREL, WDTPW and ENDINIT. Special guard bits in WDT_CON0
must be written with predefined values in order for this access to be accepted.
Valid Modify Access: A Modify Access with the correct guard bit values. The values
written to WDTREL, WDTPW, and ENDINIT are in effect after completion of this access.
Bit WDTLCK is automatically set to 1 after this access. Register WDT_CON0 is locked
until it is re-opened with a Valid Password Access again.
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