NEC 78K0 Series User Manual page 549

(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> Set bit 7 (LVION) of LVIM to 1 (enables LVI operation).
<4> Use software to wait for an operation stabilization time (10
<5> Confirm that "input voltage from external input pin (EXLVI) ≥ detection voltage (V
bit 0 (LVIF) of LVIM.
<6> Clear the interrupt request flag of LVI (LVIIF) to 0.
<7> Release the interrupt mask flag of LVI (LVIMK).
<8> Clear bit 1 (LVIMD) of LVIM to 0 (generates interrupt signal when supply voltage (V
voltage (V )) (default value).
LVI
<9> Execute the EI instruction (when vector interrupts are used).
Figure 24-8 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
• 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.
CHAPTER 24 LOW-VOLTAGE DETECTOR
Preliminary User's Manual U17260EJ3V1UD
µ
s (MAX.)).
EXLVI
.
DD
= 1.21 V (TYP.)" at
) < detection
DD
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