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CHAPTER 20 POWER-ON-CLEAR CIRCUIT
User’s Manual U19678EJ1V1UD
924
Figure 20-2. Timing of Generation of Internal Reset Signal by Power-on-Clear Circuit
and Low-Voltage Detector
Internal high-speed
oscillation clock (fIH)
High-speed
system clock (fMX)
(when X1 oscillation
is selected)
Starting oscillation is
specified by software
VPDR = 1.59 V (TYP.)
VLVI
Operation
stops
VPOR = 1.61 V (TYP.)
Starting oscillation is
specified by software
CPU
Supply voltage
(VDD)
2.7 VNote 1
0.5 V/ms (MIN.)
Note 2
3.6 ms (MAX.)
Note 2
Starting oscillation is
specified by software
Wait for oscillation
accuracy stabilizationNote 4
Wait for oscillation
accuracy stabilizationNote 3
Wait for oscillation
accuracy stabilizationNote 3
Reset processing (about 195 to 341 s)
Set LVI to be
used for reset
Set LVI to be
used for reset
Set LVI to be
used for interrupt
Normal operation
(internal high-speed
oscillation clock)Note 5
Operation stops
Reset
period
(oscillation
stop)
Reset
period
(oscillation
stop)
Normal operation
(internal high-speed
oscillation clock)Note 5
Normal operation
(internal high-speed
oscillation clock)Note 5
Reset processing
(about 2.1 to
5.8 ms)
Reset processing
(about 2.1 to
5.8 ms)
Internal reset signal
μ
Notes 1.
The operation guaranteed range is 2.7 V
≤ VDD ≤ 5.5 V. Make sure to perform normal operation after
the supply voltage has become at least 2.7 V. To make the state at lower than 2.7 V reset state when
the supply voltage falls, use the reset function of the low-voltage detector, or input the low level to the
RESET pin.
2.
Set so that no more than 3.6 ms elapses between when power is applied and when the voltage
reaches 2.7 V. If more time is required (if the voltage needs to rise more slowly than the 0.5 V/ms
(MIN.) rating), be sure to input a low level to the RESET pin before the voltage reaches 2.7 V after
power application(For supply voltage rise time timing and power supply voltage rise inclination, see
CHAPTER 28 ELECTRICAL SPECIFICATIONS).
3.
The reset processing time, such as when waiting for internal voltage stabilization, includes the
oscillation accuracy stabilization time of the internal high-speed oscillation clock.
4.
The internal reset processing time includes the oscillation accuracy stabilization time of the internal
high-speed oscillation clock.
5.
The internal high-speed oscillation clock and a high-speed system clock or subsystem clock
Note 6 can be
selected as the CPU clock. To use the X1 clock, use the OSTC register to confirm the lapse of the
oscillation stabilization time. To use the XT1 clock
Note 6, use the timer function for confirmation of the
lapse of the stabilization time.
6.
The 78K0R/IB3 doesn’t have the subsystem clock (XT clock).
Caution
Set the low-voltage detector by software after the reset status is released (see CHAPTER 21
LOW-VOLTAGE DETECTOR).
Remark
VLVI:
LVI detection voltage
VPOR: POC power supply rise detection voltage
VPDR: POC power supply fall detection voltage