RL78/G13 CHAPTER 5 CLOCK GENERATOR
R01UH0146EJ0100 Rev.1.00 308
Sep 22, 2011
Figure 5-14. Clock Generator Operation When Power Supply Voltage Is Turned On
Note 1
Power supply
voltage (V
DD
)
Internal reset signal
CPU clock
High-speed on-chip
oscillator clock (f
IH
)
High-speed
system clock (f
MX
)
(when X1 oscillation
selected)
Subsystem clock (f
SUB
)
(when XT1 oscillation
selected)
Reset processing
Note3
Switched by software
Subsystem
clock
High-speed
system clock
high-speed on-chip
oscillator clock
X1 clock
oscillation stabilization time
Note 2
Starting X1 oscillation
is specified by software.
Starting XT1 oscillation
is specified by software.
<4>
<4>
<5> <5>
<1>
<2>
<3>
0 V
1.51 V
(TYP.)
1.6 V
<1> When the power is turned on, an internal reset signal is generated by the power-on-reset (POR) circuit.
<2> When the power supply voltage exceeds 1.51 V (TYP.), the reset is released and the high-speed on-chip
oscillator automatically starts oscillation.
<3> The CPU starts operation on the high-speed on-chip oscillator clock after a reset processing such as waiting for
the voltage of the power supply or regulator to stabilize has been performed after reset release.
<4> Set the start of oscillation of the X1 or XT1 clock via software (see 5.6.2 Example of setting X1 oscillation
clock and 5.6.3 Example of setting XT1 oscillation clock).
<5> When switching the CPU clock to the X1 or XT1 clock, wait for the clock oscillation to stabilize, and then set
switching via software (see 5.6.2 Example of setting X1 oscillation clock and 5.6.3 Example of setting XT1
oscillation clock).
Notes 1. The internal reset processing time includes the oscillation accuracy stabilization time of the high-speed on-
chip oscillator clock.
2. When releasing a reset, confirm the oscillation stabilization time for the X1 clock using the oscillation
stabilization time counter status register (OSTC).
3. Reset processing time: 387 to 720
μ
s (When LVD is used)
155 to 407
μ
s (When LVD off)
Caution It is not necessary to wait for the oscillation stabilization time when an external clock input from the
EXCLK pin is used.
<R>
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