ST10F272M datasheet(91/175 Pages) STMICROELECTRONICS

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ST10F272M

System reset

91/176

Figure 26.

SW / WDT unidirectional RESET (EA = 0)

20.6

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 eight

TCL periods after the internal reset sequence completion (refer to Figure 21 and

Figure 22), 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 four TCL periods (minimum time to recognize a Short

Hardware reset) after the reset exiting (refer to Figure 27 and Figure 28), the Software

or Watchdog Reset become a Short Hardware Reset. On the contrary, if RSTF remains

low for less than 4 TCL, the device simply exits reset state.

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

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