Section 14 Power-On Reset and Low-Voltage Detection Circuits (H8/38124 Group Only)
Rev. 7.00 Mar 10, 2005 page 450 of 652
REJ09B0042-0700
Operation and Cancellation Setting Procedure Using LVDR and LVDI:
Settings should be made as indicated below in order to ensure proper operation of the low voltage
detection circuit or to cancel operation. Figure 14.7 shows the setting timing for low voltage
detection circuit operation and cancellation.
1. To turn on the low voltage detection circuit, first set the LVDE bit in LVDCR to 1.
2. After waiting for LVDCNT overflow, etc., to ensure that the stabilization time (t
LVDON
= 150
µs) for the reference voltage and low voltage detection power supply has elapsed, clear bits
LVDDF and LVDUF in LVDSR to 0. If necessary, set the LVDRE, LVDDE, and LVDUE bits
in LVDCR to 1.
3. To cancel operation of the low voltage detection circuit, clear bits LVDRE, LVDDE, and
LVDUE to 0, then clear bit LVDE to 0. Bit LVDE should not be cleared at the same time as
bits LVDRE, LVDDE, and LVDUE to avoid malfunction.
LVDRE
LVDDE
LVDUE
t
LVDON
LVDE
Figure 14.7 Low Voltage Detection Circuit Operation and Cancellation Setting Timing
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