ST10F272M datasheet(89/175 Pages) STMICROELECTRONICS

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ST10F272M

System reset

89/176

Figure 24.

Synchronous long hardware RESET (EA = 0)

If during the reset condition (RSTIN low), RPD voltage drops below the threshold voltage (about 2.5V for

5V operation), the asynchronous reset is then immediately entered.

Minimum RSTIN low pulse duration shall also be longer than 500ns to guarantee the pulse is not masked

by theinternal filter (refer to Section 21.1).

3 to 8 TCL depending on clock source selection.

20.4

Software reset

A software reset sequence can be triggered at any time by the protected SRST (software

reset) instruction. This instruction can be deliberately executed within a program, for

example, to leave bootstrap loader mode, or on a hardware trap that reveals system failure.

On execution of the SRST instruction, the internal reset sequence is started. The

microcontroller behavior is the same as for a synchronous short reset, except that only bits

P0.12...P0.8 are latched at the end of the reset sequence, while previously latched, bits

P0.7...P0.2 are cleared (that is written at ‘1’).

A Software reset is always taken as synchronous: there is no influence on Software Reset

behavior with RPD status. In case Bidirectional Reset is selected, a Software Reset event

pulls RSTIN pin low: this occurs only if RPD is high; if RPD is low, RSTIN pin is not pulled

low even though Bidirectional Reset is selected.

P0[15:13]

not transparent

RSTF

P0[12:2]

transparent

not t.

P0[1:0]

not t.

not transparent

RST

1024+8 TCL

3..8 TCL(3)

(1) V

RPD > 2.5V Asynchronous Reset not entered

200µA Discharge

RPD

RSTOUT

At this time RSTF is sampled LOW

so it is LONG reset

(After Filter)

RSTIN

1024+8 TCL

4 TCL(2) 12 TCL

≤ 500ns

≥ 50ns

≤ 500ns

≥ 50ns

≤ 500ns

≥ 50ns

ALE

8 TCL

not t.

transparent

3..4 TCL

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