CHAPTER 19 LOW-VOLTAGE DETECTOR
Preliminary User’s Manual U16846EJ1V0UD
323
19.3 Registers Controlling Low-Voltage Detector
The low-voltage detector is controlled by the following registers.
•
Low-voltage detection register (LVIM)
•
Low-voltage detection level selection register (LVIS)
(1) Low-voltage detection register (LVIM)
This register sets low-voltage detection and the operation mode.
This register can be set by a 1-bit or 8-bit memory manipulation instruction.
RESET input clears LVIM to 00H.
Figure 19-2. Format of Low-Voltage Detection Register (LVIM)
<0>
LVIF
<1>
LVIMD
2
0
3
0
4
0
Note 2
5
0
6
0
<7>
LVION
Symbol
LVIM
Address: FFBEH After reset: 00H R/W
Note 1
LVION
Notes 3, 4
Enables low-voltage detection operation
0 Disables
operation
1 Enables
operation
LVIMD
Note 3
Low-voltage detection operation mode selection
0
Generates interrupt signal when supply voltage (V
DD
) < detection voltage (V
LVI
)
1
Generates internal reset signal when supply voltage (V
DD
) < detection voltage (V
LVI
)
LVIF
Note 5
Low-voltage detection flag
0
Supply voltage (V
DD
) > detection voltage (V
LVI
), or when operation is disabled
1
Supply voltage (V
DD
) < detection voltage (V
LVI
)
Notes 1. Bit 0 is read-only.
2. Bit 4 may be 0 or 1. This bit corresponds to the LVIE bit in the 78K0/KB1.
3. LVION and LVIMD are cleared to 0 in the case of a reset other than an LVI reset. These are
not cleared to 0 in the case of an LVI reset.
4. When LVION is set to 1, operation of the comparator in the LVI circuit is started. Use
software to instigate a wait of at least 0.2 ms from when LVION is set to 1 until the voltage is
confirmed at LVIF.
5. The value of LVIF is output as the interrupt request signal INTLVI when LVION = 1 and
LVIMD = 0.
Caution To stop LVI, follow either of the procedures below.
•
When using 8-bit manipulation instruction: Write 00H to LVIM.
•
When using 1-bit memory manipulation instruction: Clear LVION to 0.