TC1796
System Units (Vol. 1 of 2)
Watchdog Timer
User’s Manual 16-14 V2.0, 2007-07
WDT, V2.0
16.4.6.2 Normal Mode Details
Normal Mode can be entered from Time-Out Mode only if bit WDT_CON1.WDTDR is set
to 0 before proper termination of Time-Out Mode. The WDT operates as a standard
Watchdog in this mode, requiring timely service to prevent a timer overflow.
Exit 1. Writing ENDINIT to 1 with a Valid Modify Access (a Valid Password
Access must have been executed first).
2. Timer WDTTIM overflows from FFFF
H
to 0000
H
.
3. An invalid access to WDT_CON0 (either during the password or the
Modify Access).
Next
Mode
Depending on the Exit condition:
1. If WDTDR = 0 (no disable request), the WDT enters the Normal Mode
or
if WDTDR = 1 (disable request), the WDT enters the Disable Mode.
2. Bit WDTOE is set to 1, and the WDT enters the Prewarning Mode.
3. Bit WDTAE is set to 1, and the WDT enters the Prewarning Mode.
Table 16-5 WDT Normal Mode
State /
Action
Description
Entry • Only from Time-Out Mode by writing ENDINIT to 1 with a Valid Modify
Access (a Valid Password Access must have been executed first),
while bit WDTDR = 0.
Actions
on Entry
• WDTTIM is loaded with the value of WDTREL.
• Bits WDTAE, WDTOE, WDTPR, WDTTO, and WDTDS are cleared to
0.
Operation • WDTTIM starts counting up from reload value with frequency selected
through WDTIS.
Exit 1. A Valid Password Access to register WDTCON.
2. Timer WDTTIM overflows from FFFF
H
to 0000
H
.
3. An invalid access to WDT_CON0 (either during the password or the
Modify Access).
Next
Mode
Depending on Exit condition:
1. Time-Out Mode.
2. Prewarning Mode, bit WDTOE is set to 1 (overflow error).
3. Prewarning Mode, bit WDTAE is set to 1 (access error).
Table 16-4 WDT Time-Out Mode (cont’d)
State /
Action
Description
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