Operation Of Low-Voltage Detector - NEC 78K0S/KB1+ User Manual

17.4 Operation of Low-Voltage Detector

The low-voltage detector can be used in the following two modes.
• Used as reset
Compares the supply voltage (V
V < V , and releases internal reset when V
DD LVI
• Used as interrupt
Compares the supply voltage (V
when V < V .
DD LVI
The operation is set as follows.
(1) When used as reset
• When starting operation
<1> Mask the LVI interrupt (LVIMK = 1).
<2> Set the detection voltage using bits 3 to 0 (LVIS3 to LVIS0) of the low-voltage detection level select
register (LVIS).
<3> Set bit 7 (LVION) of LVIM to 1 (enables LVI operation).
<4> Use software to instigate a wait of at least 0.2 ms.
<5> Wait until "supply voltage (V
<6> Set bit 1 (LVIMD) of LVIM to 1 (generates internal reset signal when supply voltage (V
voltage (V )).
LVI
Figure 17-4 shows the timing of generating the internal reset signal of the low-voltage detector. Numbers <1>
to <6> in this figure 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
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 LVION to 0 in that order.
•
260
CHAPTER 17 LOW-VOLTAGE DETECTOR
) and detection voltage (V
DD
≥ V
.
DD LVI
) and detection voltage (V
DD
) ≥ detection voltage (V
DD
) ≥ detection voltage (V
DD
User's Manual U17446EJ3V1UD
), and generates an internal reset signal when
LVI
), and generates an interrupt signal (INTLVI)
LVI
)" at bit 0 (LVIF) of LVIM is confirmed.
LVI
) when LVIM is set to 1, an internal reset
LVI
) < detection
DD