Figure 17.5 Operational Timing Of Lvdi Circuit - Renesas H8/36912 Series User Manual

Vcc
LVDDE
LVDDF
LVDUE
LVDUF
Low Voltage Detection Interrupt (LVDI) Circuit
(When Voltages Input via ExtU and ExtD Pins are used for Detection):
Figure 17.6 shows the timing of the LVDI circuit. The LVDI circuit is enabled after a power-on
reset, however, the interrupt request is disabled. To enable the LVDI, the LVDDF and LVDUF
bits in LVDSR must be cleared to 0 and the LVDDE or LVDUE bit in LVDCR must be set to 1.
When using external compared voltage, write 0 to the VDDII bit in LVDCR, and wait for 50 µs
(t ) given by a software timer until the detection circuit has settled. Then clear the LVDDF
LVDON
and LVDUF bits to 0 and set the LVDDE or LVDUE bit to 1. After that, the output settings of
ports must be made. The initial value of the external compared voltages input on the ExtU and
ExtD pins must be higher than the Vexd voltage.
To cancel the LVDI, follow the procedures written in section 17.3.2 (4), Operating Procedures for
Enabling/Disabling LVDR and LVDI Circuits.
When the external comparison voltage of ExtD pin falls below the Vexd (D) (Typ. = 1.15 V)
voltage, the LVDI clears the LVDINT signal to 0 and sets the LVDDF bit in LVDSR to 1. If the
LVDDE bit is 1 at this time, an IRQ0 interrupt request is generated. In this case, the necessary
data must be saved in the external EEPROM, and a transition to standby mode or subsleep mode
must be made. 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 the Vreset1 (Typ. = 2.3 V) voltage and the
input voltage of the ExtU pin rises above Vexd (Typ. = 1.15 V) voltage, the LVDI circuit 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 generated.
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IRQ0 interrupt generated IRQ0 interrupt generated

Figure 17.5 Operational Timing of LVDI Circuit

Vint (U)
Vint (D)
Vreset1
VSS
Rev. 1.00, 11/03, page 275 of 376