CHAPTER 17 LOW-VOLTAGE DETECTOR
Preliminary User’s Manual U19014EJ1V0UD
440
17.4.1 When used as reset
(1) When detecting level of supply voltage (V
DD
)
•
When
starting
operation
<1> Mask the LVI interrupt (LVIMK = 1).
<2> Set the detection voltage using bit 0 (LVIS0) of the low-voltage detection level selection register (LVIS).
<3> Set bit 7 (LVION) of LVIM to 1 (enables LVI operation).
<4> Use software to wait for an operation stabilization time (10
µ
s (MAX.)).
<5> Wait until it is checked that (supply voltage (V
DD
)
≥
detection voltage (V
LVI
)) by bit 0 (LVIF) of LVIM.
<6> Set bit 1 (LVIMD) of LVIM to 1 (generates internal reset signal when supply voltage (V
DD
) < detection
voltage (V
LVI
)).
Figure 17-5 shows the timing of the internal reset signal generated by the low-voltage detector. The numbers
in this timing chart correspond to <1> to <6> above.
Cautions 1. <1> must always be executed. When LVIMK = 0, an interrupt may occur immediately
after the processing in <3>.
2. If supply voltage (V
DD
)
≥
detection voltage (V
LVI
) when LVIMD is set to 1, an internal reset
signal is not generated.
•
When stopping operation
Either of the following procedures must be executed.
•
When using 8-bit memory manipulation instruction:
Write 00H to LVIM.
•
When using 1-bit memory manipulation instruction:
Clear LVIMD to 0 and then LVION to 0.
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