CHAPTER 16 POWER-ON-CLEAR CIRCUIT
Preliminary User’s Manual U19014EJ1V0UD
432
Figure 16-2. Timing of Generation of Internal Reset Signal by Power-on-Clear Circuit
and Low-Voltage Detector
In 2.7 V/1.59 V POC mode (option byte: POCMODE = 1)
Internal high-speed
oscillation clock (f
RH
)
High-speed
system clock (f
XH
)
(when X1 oscillation
is selected)
Starting oscillation is
specified by software.
Internal reset signal
2.7 V (TYP.)
V
POC
= 1.59 V (TYP.)
V
LVI
Operation
stops
Normal operation
(internal high-speed
oscillation clock)
Note 2
Normal operation
(internal high-speed
oscillation clock)
Note 2
Operation stops
Reset period
(oscillation
stop)
Reset period
(oscillation
stop)
Normal operation
(internal high-speed
oscillation clock)
Note 2
Starting oscillation is
specified by software.
Starting oscillation is
specified by software.
CPU
0 V
Supply voltage
(V
DD
)
1.8 V
Note 1
Wait for oscillation
accuracy
stabilization
Wait for oscillation
accuracy
stabilization
Wait for oscillation
accuracy
stabilization
Reset processing (20 s (TYP.))
µ
Reset processing (20 s (TYP.))
µ
Reset processing (20 s (TYP.))
µ
Set LVI to be
used for reset
Set LVI to be
used for reset
Set LVI to be
used for interrupt
Notes 1.
The operation guaranteed range is 1.8 V
≤
V
DD
≤
5.5 V. To make the state at lower than 1.8 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.
The internal high-speed oscillation clock and a high-speed system clock 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.
Caution Set the low-voltage detector by software after the reset status is released (see CHAPTER 17
LOW-VOLTAGE DETECTOR).
Remarks
1.
V
LVI
:
LVI detection voltage
2.
V
POC
: POC
detection
voltage
3.
For
the
µ
PD78F0730, be sure to set the 2.7 V/1.59 V POC mode by using the option byte
(POCMODE = 1).
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