CHAPTER 24 LOW-VOLTAGE DETECTOR
Preliminary User’s Manual U17260EJ3V1UD
540
(3) Port mode register 12 (PM12)
When using the P120/EXLVI/INTP0 pin for external low-voltage detection potential input, set PM120 to 1. At this
time, the output latch of P120 may be 0 or 1.
PM12 can be set by a 1-bit or 8-bit memory manipulation instruction.
Reset signal generation sets PM12 to FFH.
Figure 24-4. Format of Port Mode Register 12 (PM12)
0
PM120
1
PM121
2
PM122
3
PM123
4
PM124
5
1
6
1
7
1
Symbol
PM12
Address: FF2CH After reset: FFH R/W
PM12n
P12n pin I/O mode selection (n = 0 to 4)
0
Output mode (output buffer on)
1
Input mode (output buffer off)
24.4 Operation of Low-Voltage Detector
The low-voltage detector can be used in the following two modes.
(1) Used as reset
•
If LVISEL = 0, compares the supply voltage (V
DD
) and detection voltage (V
LVI
), generates an internal reset
signal when V
DD
< V
LVI
, and releases internal reset when V
DD
≥
V
LVI
.
•
If LVISEL = 1, compares the input voltage from external input pin (EXLVI) and detection voltage (V
EXLVI
= 1.21
V
(TYP.)), generates an internal reset signal when EXLVI < V
EXLVI
, and releases internal reset when EXLVI
≥
V
EXLVI
.
(2) Used as interrupt
•
If LVISEL = 0, compares the supply voltage (V
DD
) and detection voltage (V
LVI
), and generates an interrupt
signal (INTLVI) when V
DD
< V
LVI
.
•
If LVISEL = 1, compares the input voltage from external input pin (EXLVI) and detection voltage (V
EXLVI
= 1.21
V
(TYP.)), and generates an interrupt signal (INTLVI) when EXLVI < V
EXLVI
.
Remark
LVISEL: Bit 2 of low-voltage detection register (LVIM)