C161 Datasheet, PDF (268/400 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontroller

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13.2
Reset Source Indication
The reset indication flags in register WDTCON provide information on the source for the
last reset. As the C161PI starts executing from location 00’0000_H after any possible reset
event the initialization software may check these flags in order to determine if the recent
reset event was triggered by an external hardware signal (via RSTIN), by software itself
or by an overflow of the watchdog timer. The initialization (and also the further operation)
of the microcontroller system can thus be adapted to the respective circumstances, e.g.
a special routine may verify the software integrity after a watchdog timer reset.
The reset indication flags are not mutually exclusive, i.e. more than one flag may be set
after reset depending on its source. The table below summarizes the possible
combinations:
Table 13-2 Reset Indication Flag Combinations
Reset Indication Flags¹⁾
Event
LHWR
SHWR
SWR
WDTR
Long Hardware Reset
1
1
1
0
Short Hardware Reset
*
1
1
0
Software Reset
*
*
1
-
Watchdog Timer Reset
*
*
1
1
EINIT instruction
0
0
0
-
SRVWDT instruction
-
-
-
0
1) _{Description of table entries:}
’1’ = flag is set, ’0’ = flag is cleared, ’-’ = flag is not affected,
’*’ = flag is set in bidirectional reset mode, not affected otherwise.
Long Hardware Reset is indicated when the RSTIN input is still sampled low (active) at
the end of a hardware triggered internal reset sequence.
Short Hardware Reset is indicated when the RSTIN input is sampled high (inactive) at
the end of a hardware triggered internal reset sequence.
Software Reset is indicated after a reset triggered by the excution of instruction SRST.
Watchdog Timer Reset is indicated after a reset triggered by an overflow of the
watchdog timer.
Note: When bidirectional reset is enabled the RSTIN pin is pulled low for the duration of
the internal reset sequence upon any sort of reset.
Therefore always a long hardware reset (LHWR) will be recognized in any case.
User’s Manual
13-6
1999-08