CHAPTER 22 LOW-VOLTAGE DETECTOR
Preliminary User’s Manual U16315EJ1V0UD
374
22.4 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
DD
) and detection voltage (V
LVI
), and generates an internal reset signal when
V
DD
< V
LVI
.
•
Used as interrupt
Compares the supply voltage (V
DD
) and detection voltage (V
LVI
), and generates an interrupt signal (INTLVI)
when V
DD
< V
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 2 to 0 (LVIS2 to LVIS0) of the low-voltage detection level selection
register (LVIS).
<3>
Set bit 4 (LVIE) of the low-voltage detection register (LVIM) to 1 (enables reference voltage generator
operation).
<4>
Use software to instigate a wait of at least 2 ms.
<5>
Set bit 7 (LVION) of LVIM to 1 (enables LVI operation).
<6>
Use software to instigate a wait of at least 0.2 ms.
<7>
Confirm that “supply voltage (V
DD
) > detection voltage (V
LVI
)” at bit 0 (LVIF) of LVIM.
<8>
Set bit 1 (LVIMD) of LVIM to 1 (generates internal reset signal when supply voltage (V
DD
) < detection
voltage (V
LVI
)).
Cautions 1. <1> must always be executed. When LVIMK = 0, an interrupt may occur immediately
after the processing in <5>.
2. If “use POC” is selected by a mask option, procedures <3> and <4> are not required.
3. If supply voltage (V
DD
) > detection voltage (V
LVI
) when LVIM 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, LVION to 0, and LVIE to 0 in that order.