NEC 78K0 User Manual page 369

(2) When used as interrupt
• 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
<8> Clear the interrupt request flag of LVI (LVIIF) to 0.
<9> Release the interrupt mask flag of LVI (LVIMK).
<10> Execute the EI instruction (when vectored interrupts are used).
Figure 21-5 shows the timing of the interrupt signal generated by the low-voltage detector. The numbers in
this timing chart correspond to <1> to <9> above.
Caution If "POC used" is selected by a mask option, procedures <3> and <4> are not required.
• 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 first, and then clear LVIE to 0.
CHAPTER 21 LOW-VOLTAGE DETECTOR
) > detection voltage (V
DD
User's Manual U16227EJ2V0UD
)" at bit 0 (LVIF) of LVIM.
LVI
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