Datasheet

78K0/Kx2-L CHAPTER 22 LOW-VOLTAGE DETECTOR
R01UH0028EJ0400 Rev.4.00 683
Sep 27, 2010
22.4.2 When used as interrupt
(1) When detecting level of supply voltage (V
DD)
(a) When LVI default start function stopped is set (LVISTART = 0)
• When starting operation
<1> Mask the LVI interrupt (LVIMK = 1).
<2> Clear bit 2 (LVISEL) of the low-voltage detection register (LVIM) to 0 (detects level of supply voltage
(V
DD)) (default value).
<3> Set the LVI detection voltage using bits 3 to 0 (LVIS3 to LVIS0) of the low-voltage detection level
selection register (LVIS).
<4> Clear bit 1 (LVIMD) of LVIM to 0 (generates interrupt signal when the level is detected)
(default value).
<5> Set bit 7 (LVION) of LVIM to 1 (enables LVI operation).
<6> Use software to wait for an operation stabilization time (10
μ s (MAX.)).
<7> Confirm that “supply voltage (V
DD) ≥ LVI detection voltage (VLVI)” when detecting the falling edge of VDD,
or “supply voltage (V
DD) < LVI detection voltage (VLVI)” when detecting the rising edge of VDD, at bit 0
(LVIF) of LVIM.
<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 vector interrupts are used).
Figure 22-8 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.
• 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.