ST10F272M_12 datasheet(90/176 Pages) STMICROELECTRONICS

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System reset

ST10F272M

90/176

Doc ID 12968 Rev 3

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

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