CHAPTER 23 POWER-ON-CLEAR CIRCUIT
Preliminary User’s Manual U17260EJ3V1UD
532
Figure 23-2. Timing of Generation of Internal Reset Signal by Power-on-Clear Circuit
and Low-Voltage Detector (1/2)
(1) In 1.59 V POC mode (option byte: POCMODE = 0)
Internal high-speed
oscillation clock (f
RH
)
High-speed
system clock (f
XH
)
(when X1 oscillation
is selected)
Starting oscillation is
specified by software.
V
POC
= 1.59 V (TYP.)
V
LVI
Operation
stops
Wait for voltage
stabilization
(3.24 ms (TYP.))
Normal operation
(internal high-speed
oscillation clock)
Note 3
Operation stops
Reset period
(oscillation
stop)
Reset period
(oscillation
stop)
Wait for oscillation
accuracy
stabilization
Normal operation
(internal high-speed
oscillation clock)
Note 3
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 voltage
stabilization
(3.24 ms (TYP.))
Normal operation
(internal high-speed
oscillation clock
)
Note 3
0.5 V/ms (MAX.)
Note 2
Wait for oscillation
accuracy
stabilization
Set LVI to be
used for reset
Set LVI to be
used for reset
Set LVI to be
used for interrupt
Wait for oscillation
accuracy
stabilization
Internal reset signal
Reset processing (20 s (TYP.))
µ
Reset processing (20 s (TYP.))
µ
Reset processing (20 s (TYP.))
µ
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.
If the voltage rises to 1.8 V at a rate slower than 0.5 V/ms (MAX.) on power application, input a low
level to the RESET pin after power application and before the voltage reaches 1.8 V, or set the 2.7
V/1.59 V POC mode by using an option byte (POCMODE = 1).
3.
The internal high-speed oscillation clock and a high-speed system clock or subsystem 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. To use the XT1 clock, use the timer function for confirmation of the lapse
of the stabilization time.
Caution Set the low-voltage detector by software after the reset status is released (see CHAPTER 24
LOW-VOLTAGE DETECTOR).
Remark
V
LVI
: LVI detection voltage
V
POC
: POC detection voltage