CHAPTER 23 LOW-VOLTAGE DETECTOR
User’s Manual U19780EJ2V0UD
581
(2) When detecting level of input voltage from external input pin (EXLVI)
•
When
starting
operation
<1> Mask the LVI interrupt (LVIMK = 1).
<2> Set bit 2 (LVISEL) of the low-voltage detection register (LVIM) to 1 (detects level of input voltage from
external input pin (EXLVI)).
<3> Clear bit 1 (LVIMD) of LVIM to 0 (generates interrupt signal when the level is detected) (default value).
<4> Set bit 7 (LVION) of LVIM to 1 (enables LVI operation).
<5> Use software to wait for an operation stabilization time (10
μ
s (MIN.)).
<6> Confirm that “input voltage from external input pin (EXLVI)
≥
detection voltage (V
EXLVI
= 1.21 V (TYP.)”
when detecting the falling edge of EXLVI, or “input voltage from external input pin (EXLVI) < detection
voltage (V
EXLVI
= 1.21 V (TYP.)” when detecting the rising edge of EXLVI, at bit 0 (LVIF) of LVIM.
<7> Clear the interrupt request flag of LVI (LVIIF) to 0.
<8> Release the interrupt mask flag of LVI (LVIMK).
<9> Execute the EI instruction (when vector interrupts are used).
Figure 23-8 shows the timing of the interrupt signal generated by the low-voltage detector. The numbers in
this timing chart correspond to <1> to <8> above.
Caution Input voltage from external input pin (EXLVI) must be EXLVI < V
DD
.
•
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 LVION to 0.