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ST10F276Z5

System reset

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19.4

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, e.g. 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.

Refer to Figure 32 and Figure 33 for unidirectional SW reset timing, and to Figure 34,

Figure 35 and Figure 36 for bidirectional.

19.5

Watchdog timer reset

When the watchdog timer is not disabled during the initialization, or serviced regularly

during program execution, it will overflow and trigger the reset sequence.

Unlike hardware and software resets, the watchdog reset completes a running external bus

cycle if this bus cycle either does not use READY, or if READY is sampled active (low) after

the programmed wait states.

When READY is sampled inactive (high) after the programmed wait states the running

external bus cycle is aborted. Then the internal reset sequence is started.

Bit P0.12...P0.8 are latched at the end of the reset sequence and bit P0.7...P0.2 are cleared

(that is written at ‘1’).

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

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

Refer to Figure 32 and Figure 33 for unidirectional SW reset timing, and to Figure 34,

Figure 35 and Figure 36 for bidirectional.

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