HD64F36022 datasheet(261/384 Pages) RENESAS

261 / 384 page

Section 15 Power-On Reset and Low-Voltage Detection Circuits (Optional)

Rev. 4.00 Sep. 23, 2005 Page 235 of 354

REJ09B0025-0400

(2)

LVDI (Interrupt by Low Voltage Detect) Circuit

Figure 15.4 shows the timing of LVDI functions. The LVDI enters the module-standby state after

a power-on reset is canceled. To operate the LVDI, set the LVDE bit in LVDCR to 1, wait for 50

µs (t

LVDON) until the reference voltage and the low-voltage-detection power supply have stabilized

by a software timer, etc., then set the LVDDE and LVDUE bits in LVDCR to 1. After that, the

output settings of ports must be made. To cancel the low-voltage detection circuit, first the

LVDDE and LVDUE bits should all be cleared to 0 and then the LVDE bit should be cleared to 0.

The LVDE bit must not be cleared to 0 at the same timing as the LVDDE and LVDUE bits

because incorrect operation may occur.

When the power-supply voltage falls below Vint (D) (typ. = 3.7 V) voltage, the LVDI clears the

LVDINT signal to 0 and the LVDDF bit in LVDSR is set to 1. If the LVDDE bit is 1 at this time,

an IRQ0 interrupt request is simultaneously generated. In this case, the necessary data must be

saved in the external EEPROM, etc, and a transition must be made to standby mode or subsleep

mode. Until this processing is completed, the power supply voltage must be higher than the lower

limit of the guaranteed operating voltage.

When the power-supply voltage does not fall below Vreset1 (typ. = 2.3 V) voltage but rises above

Vint (U) (typ. = 4.0 V) voltage, the LVDI sets the

LVDINT signal to 1. If the LVDUE bit is 1 at

this time, the LVDUF bit in LVDSR is set to 1 and an IRQ0 interrupt request is simultaneously

generated.

If the power supply voltage (Vcc) falls below Vreset1 (typ. = 2.3 V) voltage, the LVDR function

is performed.

LVDINT

Vcc

Vint (D)

Vint (U)

VSS

LVDDF

LVDUE

LVDUF

IRQ0 interrupt generated IRQ0 interrupt generated

LVDDE

Vreset1

Figure 15.4 Operational Timing of LVDI Circuit

HD64F36022 Datasheet(PDF) 261 Page - Renesas Technology Corp