Datasheet

Section 26 Low-Voltage Detection Circuits
REJ09B0465-0300 Rev. 3.00 Page 855 of 982
Sep 17, 2010
H8S/20103, H8S/20203, H8S/20223, H8S/20115, H8S/20215, H8S/20235 Group
Section 26 Low-Voltage Detection Circuits
This microcontroller includes a low-voltage detection module consisting of three circuits, LVD0,
LVD1, and LVD2.
The circuits are used to prevent abnormal operation (runaway execution) from occurring due to
the power supply voltage falling and to recreate the state of the microcontroller before the power
supply voltage fell when the power supply voltage rises again.
If the power supply voltage falls below a threshold voltage set by the users application, a warning
can be given to the application so the application can shutdown in a controlled manner. If the
power supply voltage continues to fall below a second programmable threshold voltage, the device
can be safely placed in the reset state. This avoids the situation where the power supply voltage
falls below the guaranteed operating voltage and the microcontroller enters an unstable state.
Thus, system stability can be improved. If the power supply voltage rises again, active mode is
automatically entered.
The circuits monitor the power-supply voltage, and generate a reset or an interrupt when the
voltage falls below or rises above a specified value.
Figure 26.1 is a block diagram of the low-voltage detection circuits. Figures 26.2, 26.3, and 26.4
are block diagrams of the LVD2, LVD1 and LVD0 interrupt/reset generation circuits,
respectively.