HD64336901G Renesas Technology, HD64336901G Datasheet - Page 301

• Manufacturer Part Number: HD64336901G
• Description: (HD64xxx Series) 16-BIT MICROCONTROLLER
• Manufacturer: Renesas Technology

17.3.2
LVDR (Reset by Low Voltage Detection) Circuit:
Figure 17.4 shows the timing of the operation of the LVDR circuit. The LVDR circuit is enabled
after a power-on reset is released. To cancel the LVDR circuit, first the LVDRE bit in LVDCR
should be cleared to 0 and then the LVDE bit in LVDCR and, if necessary, the BGRE bit should
be cleared to 0. The LVDE and the BGRE bits must not be cleared to 0 simultaneously with the
LVDRE bit because incorrect operation may occur. To restart the LVDR circuit, set the LVDE bit
and the BGRE bit to 1, wait for 50 s (t
voltage and the low-voltage-detection power supply have settled, then set the LVDRE bit to 1.
After that, the output settings of ports must be made.
When the power-supply voltage falls below the Vreset voltage (2.3 V or 3.6 V (Typ.)), the LVDR
circuit clears the LVDRES signal to 0, and resets prescaler S. The low-voltage detection reset state
remains in place until a power-on reset is generated. When the power-supply voltage rises above
the Vreset voltage again, prescaler S starts counting. It counts 131,072 clock ( ) cycles, and then
releases the internal reset signal. In this case, the LVDE, BGRE, VDDII, LVDSEL, and LVDRE
bits in LVDCR are not initialized.
Note that if the power supply voltage (Vcc) falls below V
point, the low-voltage detection reset may not occur.
If the power supply voltage (Vcc) falls below Vpor = 100 mV, a power-on reset occurs.
V
V
PSS-reset
signal
OVF
Internal reset
signal
LVDRmin
CC
Low-Voltage Detection Circuit
Figure 17.4 Operating Timing of LVDR Circuit
LVDON
PSS counter starts
) given by a software timer until the reference
131,072 cycles
LVDRmin
Reset released
Rev. 1.00, 11/03, page 273 of 376
= 1.0 V and then rises from that
Vreset
V
SS