System reset
UM0404
DocID13284 Rev 2
Figure 201. SW / WDT unidirectional RESET (EA
=
0)
23.6 Bidirectional
reset
As shown in the previous sections, the RSTOUT pin is driven active (low level) at the
beginning of any reset sequence (synchronous/asynchronous hardware, software and
watchdog timer resets). RSTOUT pin stays active low beyond the end of the initialization
routine, until the protected EINIT instruction (End of Initialization) is completed.
The Bidirectional Reset function is useful when external devices require a reset signal but
cannot be connected to RSTOUT pin, because RSTOUT signal lasts during initialization. It
is, for instance, the case of external memory running initialization routine before the
execution of EINIT instruction.
Bidirectional reset function is enabled by setting bit 3 (BDRSTEN) in SYSCON register. It
only can be enabled during the initialization routine, before EINIT instruction is completed.
When enabled, the open drain of the RSTIN pin is activated, pulling down the reset signal,
for the duration of the internal reset sequence (synchronous/asynchronous hardware,
synchronous software and synchronous watchdog timer resets). At the end of the internal
reset sequence the pull down is released and:
•
After a Short Synchronous Bidirectional Hardware Reset, if RSTF is sampled low 8
TCL periods after the internal reset sequence completion (refer to
and
), the Short Reset becomes a Long Reset. On the contrary, if RSTF is
sampled high the device simply exits reset state.
•
After a Software or Watchdog Bidirectional Reset, the device exits from reset. If RSTF
remains still low for at least 4 TCL periods (minimum time to recognize a Short
Hardware reset) after the reset exiting (refer to
and
), the
P0[7:2]
not transparent
P0[12:8]
transparent
not t.
P0[1:0]
not t.
not transparent
RST
1024 TCL
RSTOUT
RSTIN
ALE
8 TCL
P0[15:13]
not transparent