
DocID13284 Rev 2
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UM0404
System reset
Figure 199. Synchronous long hardware RESET (EA
=
0)
23.4 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’).
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
200
μ
A 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
≤
500 ns
≥
50 ns
≤
500 ns
≥
50 ns
≤
500 ns
≥
50 ns
ALE
8 TCL
1. 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.
2. Minimum RSTIN low pulse duration should also be longer than 500ns to guarantee the pulse is not masked by the
internal filter (refer to Section 21.1).
Notes:
not t.
transparent
3. 3 to 8 TCL depending on clock source selection.
3..4 TCL